In a medium-sized bowl, sift the flour, baking soda, and salt. Set aside.
2 cups all-purpose flour, 1/2 teaspoon baking soda, 3/4 teaspoon sea salt
In a separate medium-sized bowl, cream the melted butter, brown sugar, and granulated sugar until smooth.
3/4 cup unsalted butter, 3/4 cup light brown sugar, 1/2 cup granulated sugar
Add the egg and egg yolk one at a time, beating in between. Add the vanilla extract, and beat again.
1 large egg, 1 egg yolk, 2 teaspoons vanilla extract
Working slowly, add the dry ingredients to the bowl of wet ingredients, stirring just until smooth. Be careful not to overmix!
1 3/4 cups all-purpose flour, 1/2 cup unsweetened cocoa powder, 1/2 teaspoon baking soda, Optional: 1/4 teaspoon instant coffee powder
Fold in the chocolate chips.
1 1/2 cups semi-sweet chocolate chips