Here are two really easy desserts, no mixer required. I have made brownies on Yom tov before and you could hypothetically do the same with the bars. Both are non-gebrochts, for those who care.
"Miracle" Chocolate Chips bars
Preheat oven to 375
2 cups ground almonds or walnuts (get raw and grind in food processor
1 cup brown sugar
1 cup chocolate chips
Mix all the ingredients, do not add water or oil, just keep on mixing. Bake as bars for 23 minutes or cookies for 12-15 minutes.
I got this recipe from pre-Pesach bazaar in shul one year, so the credit goes to the woman who gave out the sheets with it. If you know whom I'm talking about, please let me know. And these bars are amazing!
Super Pesach Chocolate Cake
Preheat oven to 350
1 1/2 cups of sugar
1 c oil
1/2 cup cocoa
1/2 cups nuts, chopped
3/4 cup potato starch
Mix all till smooth, like brownies, pour into 9 X 13 pan, bake for 45 minutes.
This recipe I got from Mrs. Katz in Brooklyn, a Chassidishe lady. My husband ate quite a few of his single Shabbos meals at their place, so the first year we got married, we visited them on Chol HaMoed. She asked me about Pesach and I, a new bride, told her how I do not have any good recipes. She pulled out a cookbook and gave me this recipe. Now I make it every Pesach, since it is as easy as it gets, and I can pop it in the oven in the beginning of a meal and have it ready for dessert.