Preheat oven to 350 degrees F and grease 8x8 pan. Line with parchment paper that overhangs the edge and grease top of the parchment paper.
In a double boiler or saucepan, melt 6 Tbsp of butter on low heat.
Add chocolate when butter is partially melted and stir. Remove from heat and add to mixing bowl.
Add sugar and mix, then add eggs one at a time. Add vanilla, baking powder, and salt. Mix well. Add flour, stirring until combined.
Pour batter into prepared 8x8 pan and bake 10 minutes at 350 degrees F.
Chop candy into bite-sized pieces.
Beat softened butter and sugar until light in color and texture.
Add egg and beat again. Add milk and vanilla and stir until combined. Add salt, baking powder, and baking soda and mix again.
Add flour and stir. Add candy pieces and stir just until distributed throughout.
Remove brownies from oven. Scoop Tablespoons of cookie dough onto the partially-baked brownies. Return pan to the oven and bake at 350 degrees F for 25-30 minutes. The edges should start to pull from the pan.
Let cool in the pan for 2-3 hours, then lift out using the overhanging edges of parchment paper.