Begin by setting a medium pot of water over high heat to come to a boil.
Cut the bacon into small pieces and transfer to a pan over medium heat. Stir until the bacon is cooked through then transfer to a bowl and set aside.
To make the carbonara sauce, add all the ingredients to a bowl: egg yolk, parmesan, heavy cream, garlic, and black pepper.
When the water has come to a boil, add the udon noodles and cook according to package instructions (don't add any flavor packets that may come with the noodles).
Add the cooked noodles directly into the bowl with the carbonara sauce. Quickly stir as the hot noodles will cook the egg yolk. Stir until the noodles are fully coated and the sauce is smooth and creamy.
Top with the cooked bacon pieces, green onions, egg yolk, and black pepper. Serve immediately.