3/4 cup (1 1/2 sticks) cold unsalted butter, cut into pieces, plus melted for pan
8 ounces semisweet chocolate, finely chopped
1 1/2 cups all-purpose flour
1/3 cup sugar
1/2 teaspoon salt
2 1/2 cups whole milk, room temperature
6 large eggs, room temperature
1 tablespoon pure vanilla extract