Preheat oven to 350F (175C) and line a baking sheet with parchment paper. Set aside.

In a large mixing bowl, combine the butter,cocoa powder and coffee (if using) and stir until combined. Make sure the butter has cooled/is no longer warm to the touch before proceeding.

Add sugars, egg, egg yolk, and vanilla extract and stir until well-combined.

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

Gradually add dry ingredients to wet, stirring until completely combined.

Stir in 1 cup (170g) of mini chocolate chips, chopped almonds, and mini marshmallows until combined.

Scoop dough by rounded 1 ½ Tablespoon-sized scoop and roll gently between your palms to form a ball. If there is any marshmallows peeking through the dough, you may wish to tuck it into the dough, as any exposed marshmallow will leak out when cooking (not a problem or a taste issue, but cookies just aren’t as pretty this way).

Pour the remaining 1 cup (170g of mini chocolate chips into a small dish and press the top of each cookie dough ball inot the chips. Place on baking sheet, spacing at least 2” (5cm) apart, and bake at 350F (175C) for 8-10 minutes.

If desired, sprinkle sea salt on top of cookies within a minute or two after removing from oven.

Allow cookies to cool completely on baking sheet before enjoying (they will be fragile when warm).