Preheat the oven to 350℉/180℃. Grease a muffin tin really well with oil and set aside. Melt the butter and allow it to cool as the rest of the ingredients are being measured.
1 cup unsalted butter
Add the dry ingredients together in a bowl. Stir together and set aside.
2 cups all-purpose flour, 1 1/2 tsp cornstarch, 1/2 tsp salt, 1/2 tsp baking powder, 1/2 tsp baking soda
In a large bowl, add the melted butter, brown sugar, and white sugar. Whisk for 2-3 minutes until smooth.
1/2 cup light brown sugar, 1/2 cup white sugar
Add in the egg, yolk, and vanilla. Continue whisking for another minute or two until smooth.
1 large egg yolk, 1 large egg, 1 tbsp vanilla
Add the dry and wet ingredients together. With a spatula, gently combine until a soft cookie dough forms. Do not over-mix!
Add in the coconut and chocolate chips. Stir a few times to combine it all together. Do not over-mix!
1 cup unsweetened shredded coconut, 2/3 cups semi-sweet chocolate chips
Scoop the cookie dough into each muffin tin. I like using a cookie scooper for even scoops. I scooped about 2 tbsp per cookie! Add shredded coconut and chocolate chips on top (optional).
Bake for 18-22 minutes. The cookie cups are ready when the edges are a golden brown and the middles still look slightly puffy. They will continue to bake from the heat of the pan.
When slightly cooled, gently run a knife around the edges of each one and lift the cookie cups up and out of the pan. Enjoy!