• Cook the pasta one minute shy of al dente according to the package instructions. Remove from heat, drain, and place in a large bowl. Reserve some pasta water for the sauce.
• Heat olive oil in a pan and saute the chopped onions until translucent.
• Add butter. Once it has melted, whisk in flour and continue whisking until golden and bubbly; about a minute.
• Gradually add in the milk and conitnue whisking until nice and smooth, takes about 2 minutes. Whisk in salt and pepper.
• Whisk in grated cheese in three batches. Sauce should be nice and thick. If it is too thick, you can use some of the reserve pasta water.
• Stir in the cooled pasta until combined and pasta is fully coated with the cheese sauce.

If adding sausage and jalapeno

• Heat remaining oil in a pan and saute the sausage and jalapenos over medium heat, about 3-4 minutes. Add to the pasta.

If baking

• Pour cooked mac and cheese into a grased baking dish.
• In a small bowl, combine panko crumbs, Parmesan cheese, melted butter and salt. Sprinkle over the top and bake at 350 degress F until bubbly and golden brown, about 30 minutes. Serve immediately.