Salted Butter Chocolate Chunk Shortbread

INGREDIENTS

1 cup

plus 2 tablespoons salted butter, cut into small pieces, cold

1/2 cup

granulated sugar

1/4 cup

light brown sugar

1 tsp

vanilla extract

2 1/4 cups

all-purpose flour

6 oz

semi- or bittersweet dark chocolate, chopped (you want chunks, not thin shards)

large egg

Demerara, turbinado, raw or sanding sugar, for rolling

Flaky sea salt, for sprinkling