Roast Vegetables: Pre-heat the oven to 425 degrees. Add the parsnips, onions, potatoes, and garlic to a roasting pan. Add olive oil and mix well so it all is well coated with oil and then season with salt. Top with fresh sprigs of thyme (optional). Bake for 40 minutes, stir at 20 minutes.
Cook Bacon: Meanwhile, cook 6 pieces of bacon until crispy and cool on a paper towel lined plate. Save 1 teaspoon of bacon grease. Once bacon is cool, crumble.
Make Soup: Once the veggies are roasted, heat a large soup pot over medium heat. Add the bacon grease and the roasted vegetables and mix. Add the stock, milk, celery salt, and fresh ground pepper.
Boil: Turn the heat up to medium high and bring the pot to a gentle boil for 3-4 minutes.
Blend: Remove the pot from the heat and blend with an immersion blender or add to a blender or Vitamix to blend until creamy.
Serve and Enjoy: Serve with fresh minced parsley and crumbled bacon.