In nonstick skillet, heat oil over medium heat; cook onions, garlic, carrot, celery and green pepper until softened, 5 to 8 minutes. Let cool.
In bowl, bet egg, chili sauce and 2 tablespoons water. Mix in vegetables, crumbs, salt, basil, thyme, mustard and pepper. Mix in beef. Pat into 9-inch pie plate. Bake in 350°F oven for 50 to 60 minutes or until meat thermometer registers 170°F Drain off fat.
TOPPING: Meanwhile, peel and cut potatoes into quarters. In saucepan of boiling salted water, cook potatoes for 15 to 20 minutes or until tender. Drain and return to pot. Mash with potato masher; beat in buttermilk, butter, salt and pepper. Spread over meat loaf. Broil for 1 to 2 minutes or until golden. Makes 6 servings.