Using an electric mixer, beat the butter until light and creamy. Add the sugar and beat for about 3 more minutes until batter is very light and fluffy. Beat in vanilla.

Using a heavy duty scraper, scrape down sides of bowl. With mixer on low speed, slowly add flour (or do it by hand), then add chocolate chunks and stir until blended.,

Divide dough in half, then place each half on a large piece of plastic wrap. Fold plastic over to cover dough and protect your hands from getting all sticky. Using your hands, form dough into two log shapes that are just about 2¼" in diameter. Chill until firm, about 2 hours.

Preheat oven to 350°. Line a rimmed baking sheet with parchment paper. Brush outside of logs with egg wash. Roll logs in coarse sugar.

Slice each log into ½"-thick rounds. If dough falls apart when you cut it, just squish it back together in a circle.

Arrange on prepared baking sheet about 1" apart (they won’t spread much). Sprinkle with sea salt.

Bake cookies until edges are just beginning to brown, 12–15 minutes. Let cool.