First, prepare cracker crust. Preheat oven to 350°F. Butter muffin tin and set aside.
In large bowl, combine crushed Ritz crackers, 1 cup shredded cheddar and melted butter, mixing well until mixture sticks together and resembles wet sand. Fill muffin cups with mixture, and using your fingers, press crust firmly into bottoms and halfway up sides of each muffin cup.
Cook pasta in large pot of salted, boiling water. Cook pasta for about 6 minutes (or until al dente), rinse and pour into large bowl. Immediately add Rondelé cheese, remaining 1 cup shredded cheddar and butter. Mix well until thoroughly coated.
In separate medium-sized bowl, combine eggs, milk, sour cream and salt, and mix well. Pour egg mixture into macaroni, mixing until everything is thoroughly combined. Add in bacon bits and chives and mix well.
Using cookie scoop or small spoon, fill each muffin cup with 2-3 tablespoons of macaroni mixture. Top each muffin cup with additional cheddar and chives. Bake for 20-25 minutes, or until lightly golden on top. Let cool for at least 10-15 minutes before removing from muffin pan. Use fork or butter knife to gently loosen outer edges of each mac and cheese muffin and gently remove from muffin pan.