1) Cook macaroni according to package instructions. Drain and set aside. Cook bacon until crisped. Drain on a paper towel-lined plate and chop. Line a baking tray with parchment paper.
2) In a saucepan over medium heat, melt butter. Add flour and stir to create a roux. Slowly whisk in milk. Bring to a simmer. Add cheddar cheese, and stir until cheese is melted. Add in mustard. Stir and heat until thick.
3) Pour cheese sauce over cooked macaroni. Stir to combine. Evenly spread macaroni and cheese onto lined backing tray. Chill for at least 1 hour.
4) Preheat and generously grease waffle iron.
5) Remove mac & cheese from fridge and cut into 8, even squares. Place 1 square in waffle iron, top with bacon and cheddar, cover with another square and close iron lid. Cook until cheese has crisped and it's golden brown on both sides.
6) Serve with syrup is desired and enjoy!