Preheat the oven to 375°F. Line two large, rimmed baking sheets with parchment paper and set aside.

Combine the flour, salt, and baking soda in a bowl; set aside.

In the bowl of a stand mixer fitted with the paddle attachment, beat the butter with the brown and white sugar on medium-high speed until light and fluffy, stopping the mixer and scraping down the sides of the bowl if necessary, about 2 to 3 minutes. Reduce the speed to low and beat in the eggs and vanilla until just combined, stopping the mixer and scraping down the sides of the bowl as needed. Slowly add the flour mixture and beat until just incorporated. Reduce the speed to to low, then add the chocolate chips and ¾ cup of the Chex mix until just incorporated (if you mix too much you’ll break up the chex mix). 

Using 3 tablespoons of dough at a time, roll the dough into balls. Place the balls of dough onto the reserved baking sheets about 2½ to 3 inches apart. Use the palm of your hand to gently press the cookies into 2-inch discs. Crush some more Chex mix on top of the cookies and gently press it in.

Bake until the edges are lightly browned but the center still remains soft, about 11 to 12 minutes. Transfer to a wire rack and cool completely.