Use room temperature butter to grease an 8-inch souffle mold. Add the grated Parmesan and roll around the mold to cover the sides. Cover with plastic wrap and place into the freezer for 5 minutes.
Preheat oven to 375 degrees F.
In a small saucepan, heat the butter. Allow all of the water to cook out.
In a separate bowl combine the flour, dry mustard, garlic powder, and kosher salt. Whisk this mixture into the melted butter. Cook for 2 minutes.
Whisk in the hot milk and turn the heat to high. Once the mixture reaches a boil, remove from the heat.
In a separate bowl, beat the egg yolks to a creamy consistency. Temper the yolks into the milk mixture, constantly whisking. Remove from the heat and add the cheese. Whisk until incorporated.
In a separate bowl, using a hand mixer, whip the egg whites and cream of tartar until glossy and firm. Add 1/4 of the mixture to the base. Continue to add the whites by thirds, folding very gently.
Pour the mixture into the souffle. Fill the souffle to 1/2-inch from the top. Place on an aluminum pie pan. Bake in the oven for 35 minutes.