Scoop batter into cupcake liners, no more than a scant ⅔ full.
Bake for about 15-17 minutes. Check cupcakes around 15 minutes to avoid over-baking. Insert a toothpick into the center of the cupcake, if it comes out clean it is done. Remove cupcakes from oven and allow cupcakes to cool in cupcake pan for 5 minutes; transfer to wire rack and cool completely. Cupcakes should be cooled completely before frosting.
For Chocolate Buttercream
In a large bowl using an electric mixer, cream butter until creamy and smooth. Add cocoa and vanilla extract; mix until combined.
Turn mixer on lowest speed and slowly add 2 cups of powdered sugar; mix until creamy. Scrape down bowl as necessary. Adding the powdered sugar gets dusty - place a damp towel over the top of the mixer to shield flying powdered sugar dust.
Continue to slowly add remaining powdered sugar; blend until completely combined.
Once all powdered sugar has been mixed in, add 1 tablespoon of milk at a time and mix. Continue to add and mix until desired consistency is achieved.
Frost using a decorating tip or spatula onto cooled cupcakes; top with Heath Miniatures. Eat & Enjoy!
Store Peanut Butter Heath Cupcakes in an airtight container; will keep for 3+ days.Store Chocolate Buttercream in an airtight container in the refrigerator for 1+ weeks. When you are ready to use, bring to room temperature and re-whip; adding milk as needed.¹ For a creamy buttercream use pure cane sugar powdered sugar. If it doesn't say "pure cane sugar" it is beet sugar, which can leave buttercream gritty.