Chocolate Chip Cookies with Truffle center

2 1/2 cup all-purpose flour
1/2 tsp baking soda
1/2 tsp salt
6 ounces butter, melted, not hot
7 ounces (1 packed cup) brown sugar
3 1/2 ounces (1/2 cup) granulated sugar
1 egg, room temperature
1 egg yolk, room temperature
1 tbsp vanilla extract
8 ounces (1 1/3 cup) chocolate chips

• Preheat the oven to 325 degrees Fahrenheit (162 C). Whisk together the flour, baking soda, and salt in a small bowl and set aside for now.
• In the large bowl of a stand mixer, combine the melted butter and both sugars, and mix them on medium speed with a paddle attachment until the sugars are moist. Add the egg and mix until it is well-incorporated, then add the yolk and mix well again. Add the vanilla extract. 
• With the mixer running on low, add the dry ingredients and mix just until they are almost fully incorporated and there are just a few streaks of flour remaining. Add the chocolate chips and stir them by hand, scraping down the bottom and sides of the bowl with a spatula until everything is well-mixed. 
• For the best results, chill the dough for 45 minutes, until it is firmer but still able to be rolled into balls. If it’s too hard straight from the refrigerator, let it warm up on the counter for a few minutes once you’re ready to use it.
• To form the cookies, use a cookie scoop or a large tablespoon to form a 1.5-inch ball of dough. Press your thumb in the center to create an indent and spread the cookie out a little bit. Set a chilled truffle in the center of the cookie, then place a little more dough—about the size of a quarter—on top of the truffle. Pinch the bottom and top of the cookie dough together, then roll it between your palms to make it round. Place the cookie on an ungreased parchment-lined sheet, and repeat until the sheet is filled, leaving 2-3 inches between the cookies.
• Bake the cookies at 325 F for 17 minutes, rotating halfway throughout. They’re done when the cookies have spread, have a touch of color along the outer edge, and the raw sheen is off in the center. They should still be soft in the middle.