Preheat over to 350℉ (180℃). Line 2 cookie sheets with parchment paper and set aside.
Cream butter in a mixer for 30 on low-medium speed.
1 cup unsalted butter, softened
Add white sugar and brown sugar and beat for 2-3 minutes.
½ cup white sugar, 1 cup brown sugar, lightly packed
Add eggs and vanilla and beat until combined.
2 large eggs, room temperature, 2 teaspoons vanilla extract
In a separate bowl, mix together flour, corn starch, baking soda, baking powder, and salt until combined. Add to butter mixture and beat on low until combined and no flour is visible.
2½ cups all purpose flour, 2 teaspoons corn starch, 1 teaspoon baking soda, ½ teaspoon baking powder, 1 teaspoon kosher salt
Gently fold in chocolate chunks and toffee bits until incorporated.
1 package chocolate chunks, 1 cup toffee bits
Scoop cookie dough onto baking sheets, keeping about 1-2" apart so cookies can spread.
Bake for 10-12 minutes. Remove from oven and sprinkle with flake salt as soon as they come out of the oven.
flake salt, for finishing
Place cookies on a rack to cool completely.
