A crackly top and a chewy center depend on achieving the proper proportion of fats.

In honor of President’s Day, today’s plate features all-American brownies with walnuts. I cannot tell a lie — there may or may not also be chocolate liquor disks in these patriotic pastries.

According to Cooks Illustrated, achieving the crackly crunchy top that characterizes great brownies is dependent upon creating a perfect proportion of liquid to solid fat. Fat can essentially be divided into two varieties, saturated fats (which are solid) and unsaturated fats (which are liquid). When you make brownies out of a box, the premixed powdered ingredients already contain solid saturated fats. Thus, they only need the designated amount of  vegetable oil — liquid unsaturated fats — to produce a chewy, crackly topped brownie. For best results in homemade brownies, aim for a 1:3 ration of your saturated fat, here supplied by butter, and your unsaturated vegetable oil.

Also do not substitute brown sugar or another sweetener for granulated sugar. A crackly crust forms when sugar molecules rise to the surface of the batter and dry out during baking. Brown sugar and corn syrup contain more moisture than granulated sugar.  The surface of brownies made with either of these sweeteners never dries out enough for a crisp crust to form.

So enjoy your holiday from work…and fill the melting pot with chocolate.

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All-American Brownies

Adapted from Cooks Illustrated

Ingredients

Cooking Spray

1/3 cup Dutch cocoa powder

1/2 cup plus 2 tablespoons boiling water

2 ounces chocolate liquor disks, finely chopped (your favorite high-quality bittersweet chocolate will also work)

1/2 cup plus 2 tablespoons vegetable oil

4 tablespoons unsalted melted butter

2 large egg yolks

2 large eggs

2 1/2 cups granulated sugar

2 teaspoons vanilla extract or Godiva liquor

1 3/4 cups all-purpose flour

3/4 teaspoon table salt

6 ounces bittersweet chocolate, chopped into 1/2 inch pieces

6 ounces walnuts, roughly chopped

Directions

1. Adjust oven rack to lowest position and heat oven to 350 degrees. Spray with nonstick cooking spray.
2. Whisk cocoa and boiling water together in large bowl until smooth. Add unsweetened chocolate and whisk until chocolate is melted. Whisk in melted butter and oil. The mixture may look curdled. Add eggs, yolks, and vanilla and continue to whisk until smooth and homogeneous. Whisk in sugar until fully incorporated. Add flour and salt and mix with rubber spatula until combined. Fold in bittersweet chocolate pieces.
3. Scrape batter into prepared pan and bake until toothpick inserted halfway between edge and center comes out with just a few moist crumbs attached, 30 to 35 minutes. Transfer pan to wire rack and cool 1½ hours.
4. For the chewiest texture, it is important to let the brownies cool thoroughly before cutting. Cut into 2-inch squares and serve.