12 tablespoons (1-1/2 sticks) unsalted butter
5 large eggs
2 teaspoons vanilla extract
1/2 teaspoon salt
2-1/2 cups sugar
1/3 cup light corn syrup
1-1/3 cups flour
Preheat the oven to 375 degrees. Butter a 9-by-13-inch pan. Slowly heat chocolate and butter, stir frequently. Set aside to cool. Beat eggs, vanilla, salt, sugar and corn syrup until light and fluffy. About 5 minutes with an electric mixer. Stir flour into chocolate mixture. Gently fold chocolate batter into the egg mixture. Stir until just combined. Spread batter evenly in the prepared pan.
Bake for 35 minutes, until top is crisp but a toothpick inserted in the center comes out coated with chocolate. Transfer pan to wire rack to complete cool before cutting into squares.
Store in an airtight container in the refrigerator.
