Grits: Bring 4 1/2 cups of water to a boil in a large saucepan over high heat. Whisk in the grits and salt, reduce heat to low, and cook at a gently simmer for 35 to 40 minutes or until the grits are thick, stirring occasionally. Stir more often as the grits thicken. Remove the pan from the heat, add the cheddar, parmesan, butter, pepper, and Tabasco, and stir until smooth. Taste and adjust the seasoning. Keep warm over very low heat.

Shrimp: In a medium skillet over medium-high heat, cook the bacon for 6 minutes or until crisp, stirring occasionally. Transfer with a slotted spoon to drain on paper towels and leave the fat in the skillet. If there is less than 1 1/2 tablespoons of bacon fat, make up the difference with peanut oil.

Toss the shrimp with the flour until lightly coated, shaking off any excess. In the skillet with the reserved fat, cook the shrimp over medium-high heat for 1 minute or until they begin to turn pink. Add the mushrooms and bacon and cook for 1 minute. Add the garlic and cook, stirring, for 30 seconds (do not let the garlic brown). Stir in the hot sauce, lemon juice, and scallions and remove from the heat. Divide the grits among 4 shallow bowls and top with the shrimp mixture. Garnish with additional scallions and serve at once.