Preheat oven to 350°F and line muffin tin with liners.
Mix cake mix, brownie mix, eggs, water, and oil for about 2 minutes until mostly smooth.
Pour batter into liners, filling about ⅔ full.
Bake 18–22 minutes until set and a toothpick shows moist crumbs.
Cool in pan 5 minutes, then transfer to rack and cool 30 minutes.
Mix butter, cocoa, honey, vanilla, and sugar until combined.
Add heavy cream gradually until smooth and creamy.
Frost cooled cupcakes and serve.