Set a large dutch oven over medium heat and add a splash of oil. Add the bacon and fry slowly to render the fat and make it crispy. Remove the bacon from the pot with a slotted spoon and set it aside to cool before chopping.
Add the butter to the pot with the bacon fat, then add the leeks. Fry the leeks until they begin to soften. Add the garlic and fry for another minute until fragrant. Add the stock, thyme and potatoes and bring to a boil. Reduce the heat and cover, and cook until the potatoes are soft and break apart.
Remove the pot from the heat and blitz the potatoes with a hand blender until it is only just smooth. Over blending will cause the soup to be gummy. Add the cream and Edam cheese and stir to combine and melt the cheese.
Top the soup bowls with a sprinkling of grated Gouda, crispy bacon bits, chopped chives and croutons. Serve immediately.