Preheat the oven to 425°F. Line 24 mini muffin cups with liners and lightly spritz with cooking spray. Set aside.
In a medium size mixing bowl use a whisk to sift together the brown sugar, flour, baking powder and salt.
Make a well in the center and add the melted butter, eggs and vanilla. Use a fork to blend together just until fully moistened.
Sprinkle 1/2 of the chopped pecans into the bottom of each mini muffin liner. Divide the batter evenly between each mini muffin cup.
Sprinkle the tops with the remaining 1/2 cup chopped pecans.
Bake for 10-12 minutes or until a toothpick inserted into the center comes back clean.
Remove from the pan and cool on a cooling rack. Store at room temperature.