Preheat oven to 350F. Line two baking sheets with parchment paper and set aside. Place butter and sugar in the bowl of a large stand mixer, fitted with a paddle attachment. Mix on medium speed until creamy, about 3 minutes. Add egg, melted chocolate, and vanilla to bowl and mix until smooth.
Add flour, cocoa, oats, baking soda, and salt to mixer and mix on medium speed until dough comes together. (dough will be slightly sticky) Gently stir in chocolate chips.
Using a cookie scoop, scoop dough into 1-in balls and place on prepared baking sheets 1-2 inches apart. Bake cookies at 350F 9-10 minutes or until edges are golden (cookies will appear underdone in the middle---this ok) Cool cookies 5 minutes on baking sheet, then transfer to a wire cooling rack. Enjoy cookies warm!