Step 1

Prep the oven and baking pan. Position a rack in the center of the oven and preheat the oven to 350°F. Line a quarter or a half sheet pan with parchment paper.

Step 2

Mix the dry ingredients. In a small bowl, whisk together the flour, baking soda, and salt.

Step 3

Mix the butter, sugars, egg, and extract. In a medium bowl, use a rubber spatula to mix together the butter and sugars until moistened, about 1 minute. Add the egg yolk and vanilla extract and mix until combined.

Step 4

Add the dry ingredients and chocolate. Gradually mix in the dry ingredients until just combined. Add the chocolate all at once and mix until the chocolate is evenly distributed throughout, about 1 minute.

Step 5

Assemble the cookies. Use a 1 ½-Tablespoon cookie dough scoop to portion the cookie dough into 6 cookie dough balls OR a 3-Tablespoon cookie dough scoop to portion the cookie dough into 4 cookie dough balls. Place them at least 3 inches apart on the prepared sheet pan.

Step 6

Bake the cookies. Bake for 9 minutes if making 6 cookies OR 10 minutes if making 4 cookies, or until the edges have set but the centers are still gooey. The cookies will look puffed when you pull them out of the oven, but will fall and crack into the perfect cookies as they cool. Cool the cookies on the pan on a wire rack for 20 minutes, or until the edges and bottoms of the cookies feel firm to the touch. Repeat with remaining cookie dough balls.

Step 7

Serve and store. Serve warm or at room temperature. The cookies can be stored, in an airtight container at room temperature, for up to 3 days.