I've been using the "durable cake" recipe for white and chocolate boxed mixes and like this the best. It adds: 4 egg whites, 1/2 c water, 1/3 c oil, 1 box pudding mix, 1 c sour cream to the standard boxed mix.

By accident, I bought a ton of yellow boxed mix, but it says "butter recipe." When I used one in last week's cake (it was just one of the layers), I found it came out very different from the white/chocolate ones, using the durable recipe alteration.

What can I do to make the yellow "butter recipe" the same durable consistency as the white/chocolate mixes??

Thanks!