Preheat oven to 350 degrees and line a baking sheet with parchment paper.
Beat butter, white sugar and brown sugar on medium high until light and fluffy.
Slowly add flour and mix on low until incorporated.
Add chocolate chunks and mix just to incorporate.
Remove from mixing bowl and use hands to condense the dough into a ball.
Put dough ball into plastic wrap and form into a log with your hands and by rolling it.
Chill the plastic wrapped dough until firm (at least 2 hours or overnight).
Using a serrated knife, carefully slice the log into ½ inch thick rounds. Slice slowly, especially when hitting a chocolate chunk. If a round falls apart just press the pieces back together.
Beat egg and roll each dough round into the egg and then roll in the sugar.
Place each round on the prepared baking sheet.
Sprinkle with sea salt.
Bake until edges are just beginning to brown. 10-12 minutes
