Heat oven to 400°F. Spray 34 mini muffin cups with cooking spray. In 3-quart saucepan, cook and drain macaroni as directed on package; return to saucepan.
Meanwhile, in 1-quart saucepan, melt butter over medium-low heat. Stir in flour and salt. Cook and stir until mixture is smooth and bubbly. Gradually add milk, stirring constantly, until mixture boils and thickens. Stir in 3/4 cup of the Cheddar cheese until melted. Stir in Parmesan cheese, blue cheese and bacon until blended. Pour over macaroni, stirring until well mixed.
Spoon mixture into mini muffin cups, filling full. Sprinkle with bread crumbs. Sprinkle evenly with remaining 3/4 cup Cheddar cheese.
Bake 20 to 25 minutes or until golden brown. Let stand 10 minutes. Sprinkle with chives. Remove from pans.