In a large nonstick skillet, heat 2 tablespoons oil over medium-high heat. Add potatoes; cook until browned and tender, about 15 minutes. Let drain on paper towels.
In same skillet, heat remaining 1 tablespoon oil. Add onion, salt, and pepper; cook for 2 minutes. Add shrimp, mushrooms, leek, and cayenne; cook for 2 minutes, stirring constantly.
Add garlic and potatoes; cook for 3 minutes. Stir in butter and vermouth. Divide into 4 equal portions, and drizzle with pan sauce.
Recipe by Louisiana Cookin' at https://louisianacookin.com/shrimp-orleans/