In a small bowl, toss together the pecans, maple sugar, maple syrup, salt and cayenne. Stir to make sure all the nuts are well coated. Spread out on a parchment lined baking sheet and bake for about 10-12 minutes until bubbling and caramelized. Cool.
Butter and flour a 9-inch square brownie pan. Line the pan with parchment so that there is an overhang on two sides. (this makes lifting the brownies out of the pan much easier.)
In a large saucepan over low heat, add the butter and unsweetened chocolate and stir with a wooden spoon until completely melted. Remove the saucepan from the heat and add both of the sugars, stirring well until incorporated.
With the wooden spoon, beat in the eggs, one at a time, stirring after each addition until mixture is well blended. Stir in the salt.
Fold in the yogurt and then the flour and stir until well incorporated. Chop 1/2 cup of the pecans and fold into the batter. Pour the batter into the prepared pan. Arrange the remaining 1/2 cup pecans decoratively on top of the brownies.
Preheat oven to 350 degrees F and bake for approximately 50-55 minutes, or until a toothpick inserted into the center comes out clean.