In large pan, cover potatoes and carrots with 2 inches of cold water. Bring to boil over high heat. Simmer until vegetables are tender, about 20 minutes.
Meanwhile, cook bacon in large skillet over medium heat until crisp; drain on paper towels. Discard all but 2 tablespoons of the bacon drippings from skillet; add oil and onion to drippings, and saute 10 minutes or until softened and lightly brown. Stir in thyme and cook 2 minutes more.
When potatoes are fork tender, drain in colander and transfer mixture to large bowl. Add buttermilk, butter and salt; mash with potato masher until potatoes are smooth, with small flecks of carrot visible. Stir in onions. Crumble bacon over top.
Makes 10 side dish servings.
Please Note: Nutritional values listed may vary from final results depending on actual measurements and brands used to prepare the recipe.