BLANCH the asparagus: Bring 2-3 inches of water to boil in a wide saucepan with a lid. Prepare a bowl of ice water. Add washed asparagus to the water, close the lid, and steam the asparagus for 2-3 minutes and then transfer to ice water to stop the cooking. Drain after a few minutes and set aside.
CARAMELIZE the onions: In a sauté pan, sauté the onions in the olive oil, stirring often, until richly browned but not burnt–about 20 minutes.
Meanwhile, make MORNAY sauce: In a large saucepan on low heat, melt butter and add flour. Stir together to form a “roux” (a 1-to-1 combination flour and butter, used as a thickener). Slowly add milk and half and half, being careful that it does not boil. Stir until combined and thickened. Add oregano, salt and pepper and stir. Add cheese by the handful and stir after each handful until well melted.
MIX: In a large bowl, mix pasta and cheese. Fold in the veggies.
BAKE: 25 minutes or until golden brown on top.
Top the finished mac ‘n’ cheese (or the individual servings) with crumbled bacon.