- 1 cup butter, unsalted and at room temperature
- 1 cup light brown sugar
- ¾ cup granulated sugar
- 1 egg, plus 1 yolk
- 1 tsp vanilla extract
- 1 cups all-purpose flour
- 1 cups bread flour
- 3/4 tsp baking soda
- 3/4 tsp salt
- 2 cups milk chocolate, finely chopped (good quality, at least 35% cocoa solids)
- Pinch of sea salt flakes
- Preheat oven to 350 degrees.
- In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and both sugars on medium speed until light and fluffy, about 3 to 4 minutes. Next, add the whole egg and egg yolk then beat until combined, followed by vanilla. With the mixer on low, gradually, add the dry ingredients, beating just until incorporated.
- Divide the dough into 3 equal portions and shape each into a 4 × 6-inch rectangle. Wrap in saran wrap and refrigerate for at least an hour.
- Remove from the fridge and unwrap the dough rectangles. On a lightly floured work surface, place 1 rectangle dough and sprinkle half of the chocolate evenly over the rectangle. Top with the second piece of dough and sprinkle the remaining chocolate over the second piece of dough, then finally top with the third dough.
- Dust the top piece of dough lightly with flour, then gently roll the stack of dough until it is about 1 ½ inches thick. Use a 2-inch round cutter to cut as many rounds as possible from the dough. Transfer the rounds to a parchment-lined baking sheet, place 2 inches apart to allow spreading. You can gather all the scraps of dough together into a mound and cut additional cookies out.
- Cover the baking sheet loosely with saran wrap and refrigerate the cookies for at least an hour.
- Bake for 9 to 10 minutes until the edges of the cookies are set. The centers will seem really soft and under-baked, but they’ll set up as they cool. Allow cookies to cool for about 5 minutes before transferring them to wire racks to cool completely.