Preheat oven to 350 degrees and grease mini muffin tin generously with butter. Coat insides of mini muffin tin with breadcrumbs to help the bites hold their shape.
Bring large pot of lightly salted water to a boil and add macaroni. Cook 4-5 minutes, just until softened but not cooked through. Remove from heat, drain and return to pot.
Stir in remaining butter and egg until pasta is evenly coated. Mix in bacon, mustard, milk, salt and cheeses (reserving 1 cup Jack cheese) then spoon into muffin tin, press filling gently with fingers (to help the bites hold their shape). Top with reserved cheese.
Bake 15-20 minutes or until top is golden brown.
Allow muffins to cool slightly before removing from pan. Garnish with fresh parsley and enjoy.
Mac and cheese bites are the perfect party food–you can eat them on the go!