-
1
Position a rack in the center of the oven and preheat to 325F (160C).
-
2
Line a 13-by-9 1/2-inch baking pan with a double thickness of aluminum foil so that the foil extends 2 inches beyond the two short ends of the pan.
-
3
Fold the overhang down along the sides of the pan.
-
4
Butter the bottom of the foil-lined pan.
-
5
In a medium bowl, stir together the flour, baking soda, baking powder and salt.
-
6
Place the semisweet chocolate in a large bowl.
-
7
In a medium saucepan, combine the sugar, butter, corn syrup and water.
-
8
Cook over medium heat, stirring constantly with a wooden spoon, until the butter melts, the sugar is dissolved and the mixture comes to a boil.
-
9
Remove the pan from the heat and pour the hot syrup over the chocolate.
-
10
Let the mixture stand for 1 to 2 minutes, to melt the chocolate.
-
11
Whisk until smooth.
-
12
One at a time, whisk in the eggs, blending until smooth.
-
13
Whisk in the vanilla and the flour mixture, mixing until the batter is smooth.
-
14
Using a rubber spatula, fold in 1 cup of the walnuts and 6 ounces of the Swiss chocolate chunks.
-
15
Scrape the batter into the prepared pan and spread it evenly with a spatula.
-
16
Sprinkle the remaining 1/2 cup of walnuts and 3 ounces of chocolate chunks over the top of the batter.
-
17
Bake the brownies for 40 to 50 minutes, or until a cake tester or toothpick inserted into the center of the brownie comes out with a few moist crumbs clinging to it.
-
18
Cool the brownies in the pan set on a wire rack.
-
19
When the brownies are completely cool, cover the pan of brownies with plastic wrap and let the brownies set at room temperature for at least 6 hours or overnight.
-
20
Invert the brownies onto a large plate or cutting board.
-
21
Remove the pan and carefully peel off the foil.
-
22
Invert again onto a smooth cutting surface and cut into 24 bars.
-
23
Store the brownies at room temperature in an airtight container for up to five days.
