In a medium bowl, whisk together the flour, baking soda and salt. In a large bowl, using a handheld mixer, beat the 2 sticks of butter with the brown sugar and the 3/4 cup of granulated sugar at medium speed until fluffy, about 1 minute. Beat in the eggs and the remaining 2 teaspoons of vanilla. At low speed, beat in the flour mixture until just incorporated. Stir in the remaining 2 cups of chocolate chips. Press the cookie dough in the prepared pan in an even layer.