Combine melted butter and cocoa powder in a large mixing bowl and whisk until well combined.

Add sugars, egg, egg yolk, and vanilla extract and stir well.

In a separate, medium-sized bowl, whisk together flour, baking powder, baking soda, and salt.

Gradually add the dry ingredients to the wet ingredients, stirring until completely combined. I usually add the flour mixture in 4 parts, adding too much at once can make the dough difficult to stir and absorb the flour, as it is a more dry dough.

Cover dough with plastic wrap and chill in the refrigerator for 30 minutes. While dough is chilling, preheat oven to 350F (175C) and line a baking sheet with parchment paper.

Once chilled, scoop dough by 2 Tablespoon sized scoops and roll between your palms to form a smooth ball. Place on baking sheet, spacing cookies at least 2” (5cm) apart.

Bake in center rack of 350F (175C) preheated oven for 9-10 minutes. Within a minute of removing from the oven, use a flat surface (I use a 1-cup measuring cup or the bottom of a glass) to gently press down on the cookies, gently flattening the surfaces.

Allow cookies to cool on baking sheet for 5-10 minutes before removing to a cooling rack to cool completely before frosting.

Prepare the Frosting

In a medium-sized, microwave-safe mixing bowl, combine chocolate chips and heavy cream and microwave on high for 25 seconds. Remove from the microwave and whisk chocolate and cream together. If chocolate is not melted, return to microwave for another 10 seconds. Whisk again, If chocolate is still not melted, continue microwaving in 5 second increments until chocolate is fully melted and mixture is combined and smooth.

Add vanilla extract and salt, whisk to combine. Allow frosting to cool and thicken for 5-10 minutes before proceeding.

Once frosting has thickened enough to be spreadable and cookies are completely cooled, scoop 2-3 teaspoons of frosting on top of each cookie and spread evenly. Immediately sprinkle with candy chips.