How to Make It
Preheat the oven to 350°. In a large pot of boiling salted water, cook the macaroni until al dente. Drain well and transfer the macaroni to a bowl. Add a drizzle of olive oil and toss well.
Meanwhile, in a large, deep skillet, heat the 3 tablespoons of olive oil. Add the onion and bell pepper and cook over moderately high heat, stirring, until softened, about 5 minutes. Add the ground beef and cumin and cook over high heat, stirring occasionally, until the meat is browned and any liquid has evaporated, about 8 minutes. Add the flour and cook until no floury taste remains. Stir in the tomatoes and stock and simmer until thickened, scraping up any browned bits from the bottom of the pan, about 3 minutes.
Remove from the heat and stir in the macaroni, cream, parsley and 1 cup of the cheddar cheese. Season with salt and pepper.
Transfer the mixture to a large ceramic baking dish about 2 inches deep. Sprinkle the remaining 1 cup of cheese and panko on top. Bake for about 15 minutes, until the casserole is bubbling and the cheese is melted. Let stand for 5 minutes. Scatter the scallions on top and serve.