Step 1

Place the butter and half of the chocolate chips in a large heat-resistant bowl. Place the bowl over a pot of barely simmering water, making sure the bottom of the bowl doesn’t touch the water. Stir with a heat-resistant rubber spatula to encourage the chocolate and butter to melt. Remove from the heat when the chocolate and butter are melted.

Step 2

In the bowl of a stand mixer fitted with the paddle attachment, combine the melted chocolate mixture with the sugar on low speed. Add the eggs one at a time, mixing briefly after each addition. Add the vanilla and the sifted ingredients, continuing to mix on low speed until a uniform dough forms. Stir in the remaining chocolate chips and mix just to combine. The dough will be very sticky, almost like a cake batter.

Step 3

Transfer the dough to a separate container, cover with plastic wrap, and refrigerate for at least 1 hour or overnight.

Step 4

Place two oven racks in the middle positions and preheat the oven to 350ºF. Line two baking sheets with parchment paper.

Step 5

Remove the cookie dough from the refrigerator. Divide the dough into 16 equal portions, about 1½ ounces (42 g) each. Working quickly, roll each into a ball. Place the cookies on the prepared sheets, spaced at least 2 inches apart. They will expand and grow significantly as they bake.

Step 6

Bake for 8 minutes. Then rotate the sheets, switch their positions in the oven, and bake for another 7 to 8 minutes, until the tops of the cookies are no longer shiny (except for a few visible melty chocolate chips). Rotating and switching the sheets halfway through the baking process will ensure that the cookies bake evenly. The ideal cookie will be set around the edges with a softer, almost underdone center. Remove the cookies and let cool completely or enjoy while still slightly warm.