Bring a large pot of salted water to a boil. Add pasta and cook until al dente according to package instructions. Drain and set aside.
In a large pan over medium heat, melt butter completely. Add flour and whisk continuously for 1–2 minutes until lightly golden. Do not let it brown.
Slowly pour in warm milk while whisking continuously to avoid lumps. Cook for 3–5 minutes until the sauce thickens and becomes smooth.
Add minced garlic, salt, black pepper, oregano, and chili flakes. Stir well and let simmer gently.
Stir in grated cheese and mix until fully melted and smooth.
Add cooked pasta and optional vegetables or protein. Toss gently until everything is evenly coated.
If sauce is too thick, add a splash of warm milk and stir.
Garnish with extra cheese or fresh parsley and serve hot.