Heat a large Dutch oven over medium-high heat. Add 1 1/2 teaspoons oil to pan; swirl to coat. Add onion, thyme, and garlic; sauté 5 minutes or until tender, stirring occasionally. Add potatoes, stock, 1/2 teaspoon salt, and bay leaf; bring to a boil. Cover, reduce heat, and simmer 35 minutes or until potatoes are very tender, stirring occasionally. Remove from heat; discard bay leaf.
While potatoes simmer, combine remaining 1 tablespoon oil, cauliflower, 1/4 teaspoon salt, and 1/4 teaspoon pepper on a jelly-roll pan coated with cooking spray; toss to coat. Roast at 450° for 30 minutes or until browned, turning once.
Place cauliflower mixture and milk in a blender. Remove center piece of blender lid (to allow steam to escape); secure blender lid on blender. Place a clean towel over opening (to avoid splatters). Blend until smooth. Pour cauliflower mixture into a large bowl. Add half of potato mixture to blender; pulse 5 to 6 times or until coarsely chopped. Pour into bowl with cauliflower mixture. Repeat with remaining potato mixture. Place cauliflower-potato mixture in Dutch oven over medium heat. Stir in remaining 1/4 teaspoon salt, remaining 1/2 teaspoon pepper, 1/2 cup green onions, and fromage blanc; stir until fromage blanc melts. Ladle soup into 8 bowls. Top evenly with remaining green onions, cheese, and bacon.
MyRecipes is working with Let's Move!, the Partnership for a Healthier America, and USDA's MyPlate to give anyone looking for healthier options access to a trove of recipes that will help them create healthy, tasty plates. For more information about creating a healthy plate, visit www.choosemyplate.gov.