1 cup (170 grams) semisweet chocolate chips
1 1/2 sticks (170 grams) unsalted butter, cut into pieces
4 ounces (113 grams) unsweetened chocolate, chopped
1 1/2 cups (300 grams) granulated sugar
3 large eggs plus 1 egg yolk
1 teaspoon vanilla extract
3/4 cup (94 grams) all-purpose flour
1/4 teaspoon fine sea salt