Preheat oven to 375F (190C). Prepare large and dip baking dish, set aside.

To a large pot filled with water add 1 tablespoon of salt and bring to a boil.

Meanwhile, in a large pan, heat olive oil over medium heat. Add chopped onion and sauté for 4-5 minutes, add crushed garlic and sauté for 1-2 minutes more. Add chicken cubes and cook, stirring occasionally, until cooked, about 5-6 minutes. Then add diced bell peppers and cook for 2-3 minutes. Add tomato paste, tomato sauce, salt, pepper, paprika, oregano and stir well. Cook for 3-4 minutes and turn the heat off.

When the water is boiling, add the pasta and cook to al dente (1-2 minutes less than in the package instructions).

Meanwhile make the béchamel sauce: in a large sauce pan, melt the butter, add flour and whisk until smooth paste forms, then cook for 1 minute. Gradually add warm milk, while whisking constantly. Keep whisking over medium-high heat until the sauce is smooth and thickened. Stir in salt, pepper and nutmeg.

Add the sauce to the pasta, the add the chicken mixture. Stir until well combined.

Bake for about 25-30 minutes, until golden-brown and bubbly. Let cool slightly before serving.