Preheat your oven to 350°F and line a 9x13 inch baking dish with parchment paper, leaving some overhang on the sides for easy removal later. While the oven heats, melt 1 cup of butter together with 1 cup of chocolate chips—I do this gently over low heat or in short microwave bursts, stirring frequently to avoid scorching. Once melted and cooled slightly to room temperature, whisk in 2 cups of sugar, 1.5 teaspoons of vanilla extract, and 3 eggs until well combined. Fold in 1 cup of flour just until incorporated, being careful not to overmix. Pour this batter into your prepared pan and spread it evenly.

Bake the brownie layer for 25 minutes—it should still be slightly underdone in the center when you remove it, as it will continue cooking when the pecan topping bakes on top. While this bakes, prepare your topping mixture (see Step 3).

While the brownies bake, melt 0.75 cup of butter and combine it in a bowl with 1.25 cups of brown sugar and 1 cup of corn syrup, stirring until the sugar dissolves. In a separate small bowl, lightly beat 4 eggs to create a smooth custard-like texture—I find this makes the filling more cohesive than just dumping them in whole. Pour the egg mixture into the brown sugar mixture and whisk until fully blended. Stir in 3 tablespoons of bourbon for that classic Derby pie flavor, then fold in 1 cup of chocolate chips and 2 cups of coarsely chopped pecans until evenly distributed.

Remove the par-baked brownie layer from the oven and carefully pour the pecan-chocolate topping from Step 3 evenly over it. Return the pan to the oven and bake for 35 minutes, until the topping is set but still has a slight jiggle in the very center—this ensures a fudgy texture rather than a dry, overbaked pie. The edges should look set and slightly darker than the center.

Remove the derby pie brownies from the oven and let them cool completely at room temperature—this typically takes 2-3 hours. Cooling fully allows the layers to set properly and makes cutting much cleaner. Once cooled, use the parchment paper overhang to lift the entire dessert out of the pan, then cut into squares and serve. These actually taste even better the next day as the flavors meld together.