Salted Butter and Chocolate chunk Shortbread Cookies

Directions

Beat the butter, granulated sugar, brown sugars and vanilla with electric mixer until light and fluffy, scraping down bowl as needed. Add flour and mix until just combined. Add chocolate chunks; mix until incorporated. Mixture will look crumbly.
Divide dough between two sheets of parchment paper, waxed paper or plastic wrap and use hands to form two log shapes, about 2" in diameter. Chill until totally firm, about 2 hours.
Heat oven to 350 when ready to bake cookies. Line one or two large baking sheets with parchment paper. Lightly beat the egg; unwrap the chilled dough and brush egg over the sides. sprinkle the coarse sugar on the open paper or plastic wrap and roll the logs into it, coating them.
Using a sharp serrated knife, cut the logs into 1/2 inch thick rounds. (You are going to hit some chocolate chunks so saw gently, squeezing the cookie to keep it from breaking if needed). Arrange cookie slices on prepared cookie sheets, about 1" apart, and sprinkle each with a few flakes of salt.
Bake for 12-15 min or until edges turn golden brown. Let cool slightly in pan before transferring to a wire rack.
The dough can be made ahead of time and stored, tightly wrapped in plastic, up to 1 week in refrigerator, or 1 month in freezer. Baked cookies keep in airtight container for 5 days.