In a large Dutch oven, cook bacon over medium heat. When cooked, remove and set aside. Add leeks, celery, onions, salt, and pepper. Sauté until the leeks tender. Stir occasionally.
Add the chicken stock, chicken bouillon, thyme, and potatoes. Bring to a simmer and cook until the potatoes are fork tender about 20-25 mins stirring occasionally.
Mix the cornstarch into the heavy cream. Be sure to stir thoroughly to avoid any clumps.
Pour the cornstarch mixture into the pot of soup and stir until well combined stirring until the soup returns to a simmer. Use a potato masher to mash the potatoes until desired consistency. Stir in the bacon.
Salt and pepper to taste.
Garnish with green onions.
Serve immediately.