Preheat the oven to 375°F (190°C).
Cook the pasta in salted boiling water according to package instructions until al dente. Drain and set aside.
In a saucepan over medium heat, melt 2 tablespoons of butter. Add the chopped bacon and cook for 20–30 seconds. Add the breadcrumbs and toast, stirring well. Reduce heat to low, add the chopped parsley, mix, and remove from heat. Set aside.
In a deep saucepan, melt the remaining butter over low heat. Add the pimento peppers, bird’s eye pepper, garlic, and bell peppers. Cook for 3–4 minutes, stirring continuously.
Add the black pepper and salt to the saucepan. Stir in the flour and cook for another 3–4 minutes to eliminate the raw flour taste.
Gradually add the milk, whisking constantly to prevent lumps. If needed, return the pan to the burner for 1–2 minutes to thicken the sauce.
Remove the saucepan from heat and stir in 2/3 of the grated cheeses until melted and smooth. Add the chopped scallions and mix well.
Add the cooked pasta to the cheese sauce, folding gently to combine. Grate the nutmeg into the mixture and stir.
Grease a 9x13-inch baking dish with butter. Pour the macaroni and cheese mixture into the dish, spreading evenly.
Top the macaroni with half of the reserved cheese, followed by half of the breadcrumb mixture. Repeat with the remaining cheese and breadcrumbs.
Bake uncovered on the middle rack for 40 minutes, until the top is golden brown.
Remove from the oven and let it cool for about 10 minutes before serving.