Preheat oven to 350 degrees, spray a donut pan with nonstick spray and set aside. In a skillet over medium low heat, melt 4 tablespoons of butter and heat until it becomes frothy and begins to smell nutty. Remove from heat and set aside.
In a large bowl, blend together egg and 2 tablespoons of the browned butter. Add in yogurt, buttermilk and nutmeg then blend in dry pancake mix and stir until a batter forms.
Use a spoon to fill the prepared donut pan three-quarters full with batter, smooth batter then bake 8-10 minutes, until golden brown. Allow donuts to cool 5 minutes in the donut pan, then invert onto a wire rack and cool completely.
To make the glaze, in a medium bowl whisk together the remaining brown butter, one tablespoon of milk and the dry glaze mix. Stir until the mixture becomes smooth then use a butter knife to spread the glaze onto the top of each donut. Sprinkle chopped pistachios onto the glaze.