Boil pot of water and cook 1 lb elbow pasta accordingly.
In a large pan, fry chopped 8 slices bacon over medium-high heat for 8 minutes, then add in 2 cup corned beef, 3 medium leeks and 3 cloves garlic for another minute.
Reduce heat and toss in chopped 1 medium green cabbage. Cover and let simmer to cook and wilt green cabbage.
Cheese Sauce
In a medium pot, melt 4 Tbsp butter over medium heat and whisk in 4 Tbsp all purpose flour. Cook for a minute, be careful not to burn.
Pour in 3 cups milk and let mixture thicken as it cooks. Whisk often. When thickened, add all 6 oz monteray jack cheese, 6 oz white sharp cheddar, 6 oz harvarti cheese and mix often. Cheese should melt in about 10 minutes over medium heat.
When all components are cooked then mix everything together in a large bowl and serve hot.