In a large bowl, toss brussel sprouts with 2 tablespoons of oil, salt, and pepper. Spread onto a baking sheet.
Place sprouts into cold oven, and set oven to 450 degrees. Cook for 14-16 total minutes, stirring once. The goal is for very very crispy and brown sprouts.
As sprouts cook, whisk together mustard, maple syrup, 2 tablespoons of olive oil, and garlic salt in the biggest bowl you have. Once sprouts are cooked, quickly toss in dressed bowl and serve.