8 ounces unsalted butter (2 sticks; 225g; see note) 1 standard ice cube (about 2 tablespoons; 30mL frozen water) 10 ounces all-purpose flour (about 2 cups; 280g) 3/4 teaspoon (3g) baking soda 2 teaspoons Diamond Crystal kosher salt or 1 teaspoon table salt (4g) 100 g granulated sugar 2 large eggs (100g) 2 teaspoons (10ml) vanilla extract 100 g dark brown sugar 30 g Korean rice syrup or light corn syrup 8 ounces (225g) semisweet chocolate, roughly chopped with a knife into 1/2- to 1/4-inch chunks Coarse sea salt, for garnish