Best Bownies EVER

A new recipe my sister and I came up with:
1 box Ghirardelli Double Chocolate Brownie Mix (1 egg, 1/3c oil, 1/3c H2O)
mini Reese's Peanut Butter cups
metallic muffin liners
Frosting:
1 lb light brown sugar
1 cup heavy whipping cream
1/2 tsp baking soda
1/2 cup butter
powdered sugar

Bring brown sugar and cream to rolling boil. Boil 1 minute. Add soda. Boil 1 minute. Remove from heat. Add Butter. DO NOT STIR. Cool to room temp then place in fridge at least 1 hour until very thick. Make brownie mix according to box. Place 8 liners in muffin tin and spray lightly with cooking spray. Spoon mix into muffin cups 3/4th full. Place 1 unwrapped candy into center. Bake about 24 minutes at 350. Beat chilled, thickened frosting on high adding powder sugar as needed to thicken to spreadable consistency. Once brownies are cool, frost. Swoon.