Makes 16 large cookies
1 cup (2 sticks) unsalted butter, softened
Preheat oven to 350 F.
In a large bowl, sift together flour, baking soda, baking powder and salt and set aside.
In the bowl of an electric mixer, cream the butter and sugars together until fluffy. Beat in the eggs and vanilla and mix until combined. Slowly add flour mixture and blend until completely incorporated. Stir in chocolate and toffee.
Drop 2 ounces of cookie dough onto a baking sheet lined with parchment or into the cups of a muffin top pan. Sprinkle each cookie with a generous pinch of fleur de sel. Bake until cookies are puffed and just started to brown, 13-15 minutes. Transfer cookies to a rack to cool completely.