If you have more than a kid or two, and aren't afraid of baking, you may want to do what I did with the first child, and purchase a sheet cake pan (mine is an 11" x 15" x 2" by Wilton) and a set of decorating tips before throwing your first graduation open house. With those items, plus a frosting spreader/spatula thing, I have made three graduation cakes so far, saving myself quite a bit of money versus ordering and purchasing a bakery made cake for each open house.
My pan is a 1/2 sheet cake size, which, depending on how big you cut the pieces, serves 18-40. For an open house, we cut pieces small and get 40-50 (some people request a 1/2 size piece because they are diabetic but still want cake!) It holds a double batch of any from-scratch cake recipe I've tried in it so far. Not sure how that translates into boxed cake mixes (which have never been at this little place here, I think I stopped using them in 1997 if not earlier. . .) but I'd guess at 2-3 mixes.
Back in May, I received some coupons in the mail for my local grocery store that takes cake orders. According to those coupons, their 1/2 sheet cake starts at $25. Price goes up depending on what type of cake it is and what types of decorations you want.
For my kids' open houses, I have made the equivalent of a full sheet cake (lowest price @ store $42); baking two cakes in my pan and then either layering them, or doing two different flavors and setting them out side by side. DD1 chose a confetti (white) cake and a chocolate cake, which I converted to egg-less so her egg allergic boyfriend could have some. Anyway, had I purchased her cakes at the store, I would have spent a minimum of $50 and most likely not have been able to have the egg-less option. My ingredients for both cakes, including frosting, cost about $20 total. Yes, it did take my time to make, frost and decorate the cakes, but while baking I was able to work on other stuff, so that time is negligible. The frosting and decorating probably took an hour, which is roughly equivalent to the time I would have spent on the phone ordering the cake, then driving 20 min to pick it up after it was ready and 20 min back home. So, to me, time is not a factor, just the actual money spent. Since I buy my baking supplies in big sizes (10 lb bag of sugar, box of flax seed meal, 5 lb bag of cocoa, etc) my price of $20 is a guesstimate based on how much of each ingredient was used rather than bag of flour, bag of sugar, tin of cocoa powder, dozen eggs, etc.)
Without further ado, here are two recipes for a 1/2 sheet cake. The first is my egg-less chocolate creation, so I don't think I have to give credits to any cookbook since I changed the original recipe so much. The second is also an adaptation (since I've never seen a from scratch confetti cake recipe), but the base recipe came from the book The Best of Amish Cooking by Phyllis Pellman Good and is pretty much her Ice-Water White Cake recipe.
Egg-less Chocolate Cake
4 cups all purpose flour
4 cups sugar
1 cup shortening
1 1/2 cups water
1 1/2 cups soured milk (sour w/1 1/2 Tbsp vinegar)
2 tsp baking soda
2 tsp salt
1 tsp baking powder
1 1/2 cups cocoa
1/4 cup flax seed meal
3/4 cup water
Mix flax seed meal and water in small bowl, let sit 10 min. This is your egg substitute, so don't skip out on or try to subsitute for the flax seed meal!
Meanwhile, grease and flour your (1/2 sheet) cake pan and heat oven to 350 degrees.
Then, in a large bowl, combine all ingredients (including the flax seed mixture) and beat on low speed of a mixer for 30 seconds, scraping bowl constantly. Beat on high speed 3 minutes, scraping bowl occasionally. Pour into pan and gently jiggle pan to disperse batter evenly.
Bake in center of oven 50-60 minutes or until toothpick inserted in center of cake comes out cleanly. Remove from oven, and cool in pan on wire rack. When completely cool, loosen sides from pan with a knife and gently invert onto a cake board (which you will serve the finished cake on). Frost and decorate as desired.
1 cup (2 sticks) softened butter
4 cups sugar
7 cups cake flour (you can substitute all purpose flour; 1 cup minus 2 Tbsp for each cup of cake flour, but for this recipe I really recommend spending the extra $$ for cake flour)
1 tsp salt
2 Tbsp baking powder
3 cups ice water
1 tsp almond extract
8 egg whites, stiffly beaten
1/2 to 3/4 cup nonpareil decors
Grease and flour cake pan. Heat oven to 350 degrees.
Sift together cake flour, salt, and baking powder. In a large mixing bowl, stir together (or beat on low speed) butter and sugar until creamed and fluffy. Add the sifted mixture to the bowl alternately with the ice water, beating on medium speed until all have been combined. Then beat on high speed 2 minutes. Fold in the stiffly beaten (must beat before adding) egg whites. Gently but quickly stir in the nonpareils (quickly so they don't bleed and make the cake turn grey). Pour into cake pan, jiggle pan to disperse batter evenly.
Bake in center of oven 40-50 minutes, or until toothpick inserted in center of cake comes out cleanly. Remove from oven, cool in pan on wire rack. When completely cool, loosen sides from pan with a knife and gently invert onto a cake board. Frost and decorate as desired.
To frost the cakes, I made a chocolate frosting for the chocolate cake, and a white (vanilla) frosting for the confetti one. Both recipes are Betty Crocker's (40th Anniversary Edition Cookbook), then doubled; the chocolate one I adapted to use cocoa powder instead of melting chocolate.
2 sticks softened butter
3/4 cup cocoa
4 cups powdered sugar
1 Tbsp vanilla
4-6 Tbsp milk.
In a medium mixing bowl, stir cocoa, butter and powdered sugar together. Mixture will be dry and butter should 'disappear' rather than forming crumbles. Beat in vanilla and milk until smooth, then whip (beat on high speed) to desired consistency. Can add more milk to make thinner if desired.
Creamy Vanilla Frosting
6 cups powdered sugar
2 sticks softened butter
1 Tbsp vanilla
4-6 Tbsp milk.
In large mixing bowl, stir butter and powdered sugar together. Mixture will be dry rather than crumbly. Beat in vanilla and milk until smooth, then whip (beat on high speed) to desired consistency. Can add more milk to make thinner if desired.
To make the colored frosting for the decorative writing and edging on the cakes, I made a single recipe of the vanilla frosting (3 cups powdered sugar, 1/3 cup--5 1/3 Tbsp--butter, 1 1/2 tsp vanilla, 2-3 Tbsp milk), then divided it into the quantity I needed of each desired color (white, black, yellow; the school colors) and added gel food coloring to make the correct shade of each color before spooning into my decorating bags.
Before I made my first graduation cake in 2007, I made what I called "practice cake" (only 1/2 the recipe of batter, adjust cooking time downward to reflect shallower cake) just to see if I could get the cake out of the pan cleanly without destroying it. I didn't want to have any disasters during the crunch time of the several days immediately before the open house. On the practice cake I also frosted it and experimented with the different tips in my decorating set so I could get the hang of using the bags and tips and decide which ones I wanted to employ for the official cake. Every graduation since then, my kids have requested practice cake a week before their party! (Needless to say, I gained two pounds last week. . .too much cake.)