In a large pot heat the butter over medium heat. When melted add the chopped leeks and cook until soft, around 10 minutes. Add the garlic and cook an additional minute, until fragrant.
Add the potatoes, vegetable stock, thyme, bay leaves, salt and pepper and cook covered until the potatoes are very soft, around 15 minutes.
Remove the thyme sprigs and bay leaves from the soup and discard. Using an immersion blender, blend the soup until creamy. If you do not have an immersion blender you can use a blender and then return the blended soup back to the pot. Add the cream to the soup and stir until blended. If the soup is too thick you can add additional vegetable stock.
Garnish with fresh chives and cheddar cheese and serve hot.
