From Dying for Chocolate by Diane Mott Davidson
1/2 cup unsalted butter
1/2 cup dark brown sugar
1 cup all-purpose flour
1 -2 cup pecan halves
2 eggs (I used extra-large)
1 cup firmly packed dark brown sugar
1 teaspoon vanilla extract
1/2 teaspoon salt
1 teaspoon baking powder
Additional flour (see below)
1 cup chocolate chips
Preheat oven to 375ºF.
In a food processor, combine the first three ingredients with a metal blade until coarse crumbs are formed. (Can also be done with 2 knives or a pastry cutter).
Pat as a crust into a buttered 9x13 pan. Bake for 10 minutes. Remove from oven and cool completely. Spread pecans over cooled crust. (I used the full 2 cups.)
Beat eggs with brown sugar until thick. Add vanilla. Put salt and baking power in the bottom of a 1/4 cup measure, and then fill the rest of the measure with flour. Stir this into egg mixture. Pour this mixture over the pecans and crust. Sprinkle chips over the mixture.
Bake 20 minutes or until center is set. Let cool before cutting.
http://pattietierney.blogspot.com/2015/11/lethal-layers.html