01 - Prepare elbow macaroni according to package directions until al dente. Drain thoroughly and set aside.
02 - Cook chopped bacon in a large skillet over medium heat for 6-8 minutes until crispy. Remove with slotted spoon and drain on paper towels. Reserve 1 tablespoon bacon fat.
03 - Melt butter with reserved bacon fat in a large saucepan over medium heat. Whisk in flour and cook constantly for 1 minute to form a roux.
04 - Gradually whisk in milk until smooth. Simmer for 2-3 minutes until slightly thickened. Add cheddar, Parmesan, garlic powder, onion powder, salt, and pepper. Stir until completely melted and smooth.
05 - Add cooked macaroni and half the bacon to the cheese sauce. Stir until pasta is evenly coated.
06 - Gently fold in diced avocado and lemon juice just before serving.
07 - Plate immediately, topping with remaining bacon and fresh chives if desired.