Preheat the oven to 350°F and lightly spray an 8x8-inch baking pan with nonstick cooking spray.
Cook the elbow macaroni according to package directions until al dente, drain, and transfer to a large mixing bowl.
Warm the 2 cups of milk in a small saucepan over medium heat until hot but not boiling, then remove from heat.
Melt the 1/4 cup (1/2 stick) butter in a medium saucepan over low heat. Whisk in the 1/4 cup all-purpose flour and cook, whisking constantly, about 3 minutes until smooth and bubbly.
Gradually whisk the warmed milk into the roux, increase heat to medium-high, and bring the sauce just to a boil while stirring frequently; then reduce heat to low.
Simmer the sauce a few minutes, then stir in the 1/2 teaspoon salt, 1/2 teaspoon Tabasco, a few grinds of black pepper, and the 1/2 cup heavy whipping cream; simmer 3–4 minutes, stirring occasionally.
Add 12 ounces of the shredded sharp cheddar to the sauce and stir until melted and smooth.
Pour the cheese sauce over the drained pasta and stir until the pasta is evenly coated.
Spoon the coated pasta into the prepared baking pan and sprinkle the remaining 4 ounces of shredded cheddar evenly over the top.
Bake for 20 to 30 minutes until bubbly; if desired, broil 2–3 minutes at the end to brown the top, watching closely.