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.
05 - Add cheddar and Parmesan cheese, garlic powder, onion powder, salt, and pepper. Stir until the cheese is melted and the sauce is smooth.
06 - Add the cooked macaroni and half the bacon to the sauce, stirring to coat evenly.
07 - Gently fold in the diced avocado and lemon juice.
08 - Serve immediately, topped with the remaining bacon and fresh chives if desired.