My mom frequently made these while I was growing up. They were my favorite cookie. They're more like a brownie, actually. Each batch makes about 20.
3/4 cup white sugar
1/2 cup butter, melted
1 teaspoon vanilla extract
1 cup all-purpose flour
6 Tablespoons unsweetened cocoa powder
I'm not really sure the exact amounts for this, but here's a general idea of what I do-
Melt about 2 tablespoons of butter, add a few heaping tablespoons of cocoa and a tablespoon of water. Stir in powdered sugar until you reach the desired consistency, probably 1-1 1/2 cups. Add about 1/2 teaspoon of mint extract if you want, more if that's not strong enough. If you get it too thick, you can add milk or water until you get it right.
In a medium bowl, mix the sugar and butter together. Stir in the eggs and vanilla. Then mix in the flour, cocoa, and walnuts. Preheat the waffle iron. I prefer to use a shallow iron, which are almost impossible to find anymore. I've never tried it on the Belgian type.
Drop dough by heaping tablespoons around the waffle iron. Close the lid and cook for 1 1/2 minutes. It may take more or less time depending on the individual waffle iron. Carefully remove to rack to cool.
When cookies are cool, dip them into a chocolate glaze, then let sit until glaze is set.