Preheat oven to 350 degrees. Spray a mini muffin pan with non-stick baking spray.
Melt butter and chocolate chips in a large microwave-safe bowl in 30 second increments, until melted and smooth when mixed.
Add sugar, eggs and vanilla. Stir.
Add cocoa powder, salt, and flour and mix until smooth.
Using a small cookie scoop, or tablespoon, scoop batter into mini muffin pan.
Bake for 12 minutes. While brownies are baking, unwrap chocoalte peanut butter hearts (or cups).
Gently press a piece of candy onto each brownie bite as soon as they come out of the oven. Place pan of warm brownies in the refrigerator to speed up the cooling process (also helps the chocolate hearts keep their shape).
Allow brownie bites to cool COMPLETELY before removing from pan. To remove from pan, slide a sharp knife around the edges. The brownie bites should pop right out.