01 - Cook the macaroni according to package instructions until al dente. Drain and set aside.
02 - In a large skillet over medium heat, cook the chopped bacon until crispy, about 6–8 minutes. Remove with a slotted spoon and drain on paper towels. Reserve 1 tablespoon of bacon fat, discarding the rest.
03 - In a large saucepan, melt butter with reserved bacon fat over medium heat. Add flour and cook, whisking constantly, for 1 minute.
04 - Gradually whisk in the milk until smooth. Bring to a simmer and cook for 2–3 minutes until slightly thickened. Add cheddar and Parmesan cheese, garlic powder, onion powder, salt, and pepper. Stir until the cheese is melted and the sauce is smooth.
05 - Add the cooked macaroni and half the bacon to the sauce, stirring to coat evenly.
06 - Gently fold in the diced avocado and lemon juice. Serve immediately, topped with the remaining bacon and fresh chives if desired.