Find your biggest stockpot (this recipe makes a lot of soup). Melt the butter over medium-low heat. Slice the leeks in half, and then into half moons. Cook the leeks in the butter until they’re tender. About 5 minutes. Add the garlic. Add the flour.
Deglaze the pot with the white wine, scraping up any browned bits. Season with salt, pepper, thyme, and oregano. Add 8 cups of turkey stock, then the potatoes. Bring everything to a low simmer until the potatoes are tender. This should take 45 minutes to an hour.
Use an immersion blender or hand mixer to break up the potatoes; you want a few lumps, but not huge chunks. Your soup should start thickening up quite a bit now. Add in the cream and stir to combine. Add most of the cheeses, stirring until completely melted in, reserving a little of each for garnish when you serve. If you find that the soup is too thick still, add the remaining turkey stock, a little at a time, until you have the consistency that you are looking for. Taste test, and season with additional salt and pepper as needed.
Serve this soup as an appetizer or meal, garnished with croutons, green onion, bacon bits, and any remaining cheese.