Preheat the oven to 350 °F (177 °C) then line an 8x8-inch baking pan with parchment paper.
Make the brownies by whisking together the flour, cocoa powder, baking powder and salt in a large bowl then setting aside.
Whisk the eggs, butter, granulated sugar, brown sugar and vanilla extract together in a separate large bowl until smooth then pour it gradually into the dry ingredients and mix just until there are no more lumps.
Stir in the chocolate chips then pour the mixture into the prepared baking pan and bake for 20 minutes.
While the brownies are baking make the pecan pie later by melting the butter in a large saucepan over medium heat.
Add the eggs, brown sugar, white sugar, corn syrup and vanilla and whisk continuously over medium heat until it starts to thicken, about 15 minutes.
Whisk in the heavy cream, be careful because it may start to bubble.
Stir in the pecans then pour it over the half-baked brownies.
Bake for another 20-25 minutes or until the center is only slightly jiggly.
Let them cool for about 1 hour then slice and serve.
Notes
These brownies can be stored in an airtight container for up to five days.