Bring a large pot of water to a rolling boil and salt it generously (about 1 tbsp salt per 4–6 quarts). Add the 12 oz dried elbow macaroni and cook 1–2 minutes less than package directions until just shy of al dente. Why: pasta finished in the sauce will continue to absorb liquid; undercooking prevents mushy mac once baked/finished.

While the pasta cooks, finely dice the onion and bell peppers and mince the garlic. Heat 1 tbsp butter and 1 tbsp olive oil in a medium skillet over medium heat. Add the onion and peppers and cook, stirring occasionally, until softened and slightly caramelized, about 6–8 minutes. Add the garlic in the last 60 seconds. Why: gently caramelizing vegetables adds sweetness and depth without burning the garlic; the oil+butter combo carries flavor and prevents sticking.

Reserve 1 cup of the pasta cooking water, then drain the macaroni and set aside. Why: starchy pasta water is a powerful emulsifier that loosens the sauce and helps it cling to pasta without thinning the flavor.

Make a béchamel-based cheese sauce: In a heavy-bottomed saucepan over medium heat, melt 4 tbsp butter. Sprinkle in 2.5 tbsp flour and whisk continuously for 60–90 seconds until the raw flour taste cooks out and the roux turns pale blond. Why: to cook the flour and create a thickening base — whisking prevents lumps and the pale color keeps the sauce silky, not brown.

Slowly add the 2 cups of whole milk in a thin stream while whisking constantly to avoid lumps. Bring the mixture to a gentle simmer (do not boil) until it thickens slightly, 3–5 minutes. Stir in 1 tsp Dijon mustard, 1 tsp smoked paprika, 1 tsp kosher salt (adjust later), and 1/2 tsp freshly ground black pepper. Why: heating gently prevents curdling and allows the sauce to thicken to a velvety consistency — mustard sharpens and paprika adds smoky depth.

Remove the sauce from heat and add the shredded cheeses (8 oz cheddar + 4 oz Monterey Jack) in two additions, stirring until smooth and melted after each addition. If the sauce seems too stiff, whisk in up to 1/2 cup reserved pasta water, 1 tablespoon at a time, until it reaches a glossy, pourable consistency. Why: adding cheese off-heat keeps dairy from seizing; reserved pasta water loosens the sauce and helps bind it to the macaroni via its starch.

Fold the drained pasta and the sautéed peppers/onions into the cheese sauce. Taste and adjust seasoning with additional salt and pepper as needed. Why: folding preserves pasta shape and ensures each tube is evenly coated without breaking pasta apart.

Preheat the broiler (or oven to 425°F/220°C for a deeper, even crisp). In a small skillet, melt 2 tbsp butter and stir into 1 cup panko breadcrumbs until evenly moistened; season with a pinch of salt and a dash of smoked paprika. Why: buttering the crumbs before toasting gives them a golden, nutty flavor and crisp texture rather than drying them out in the oven alone.

Portion the mac & cheese into 4 shallow bowls or a 9×13 baking pan if you prefer to bake all at once. Sprinkle the panko evenly on top. If using the oven, bake at 425°F for 6–8 minutes until the crumbs are golden, or place under the broiler for 1–3 minutes watching carefully to avoid burning. Why: quick high heat crisps the topping and creates contrast to the silky pasta beneath.

Re-crisp your butterfly shrimp: If already cooked and chilled, arrange the 12 shrimp on a baking sheet and reheat in the oven at 400°F (200°C) for 6–8 minutes, turning once, until hot and crunchy. If you have fresh raw shrimp, coat and fry or bake according to your preferred method — cook until opaque and the coating is golden. Why: reheating in a hot oven quickly re-crisps fried shrimp without sogginess from steam created in a microwave.

Top each mac & cheese bowl with 3 crispy butterfly shrimp, a sprinkle of chopped parsley and an optional dusting of freshly grated Parmesan. Finish with a crack of fresh black pepper and serve immediately. Why: finishing herbs and a little sharp cheese brighten the rich bowl and provide aroma and contrast.