Double-Chocolate Brownies

I'm always looking for healthy brownies. I saw these from Food Network. I gave them a try, they where good, not THE BEST brownies I ever had, I think I actually overcooked them by about 5 minutes. But for a heart healthy treat, I'd make them again.
Ellie Krieger's Double-Chocolate Brownies
Makes 24 brownies
Cooking Spray
6 oz bittersweet chocolate, coarsely chopped
2 tablespoons unsalted butter
1/2 cup each whole wheat and all-purpose flour
1/4 cup unsweetened cocoa powder
1/4 teaspoon salt
1/4 teaspoon baking soda
4 large eggs
1 cup packed light brown sugar
1/2 cup plain low-fat yogurt
1/4 cup canola oil
2 teaspoons vanilla extract
3/4 cup chopped walnuts (optional) (I used pecans)
Preheat oven to 350 degrees. Coat a 9x13 inch baking dish with cooking spray.
Melt the chocolate and butter in a heatproof bowl set over a saucepan of barley simmering water, stirring occasionally, do not let the bottom of the bowl touch the water.

Whisk the flour, cocoa, salt and baking soda in a medium bowl. In a large bowl, whisk the eggs and brown sugar until smooth, then add the yogurt, oil and vanilla and whisk to combine. Whisk in the melted chocolate mixture until blended. Add the dry ingredients and mix just until moistened.

Spread the batter in the prepared pan and sprinkle with walnuts, if desired. Bake for 20 to 25 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs. Cool completely in the pan on a rack before slicing.
Calories per brownie (with nuts) 160
ENJOY!