Preheat oven to 450° F. Brush 9 inch springform pan with oil.

Stack 6 chard leaves on cutting board, and roll tightly into cylinder. Slice cylinder to chiffonade leaves into thin strands. Repeat with remaining leaves

Place 1 sweet potato slice in center of bottom of prepared springform pan. Arrange slices in circles around center slice, overlapping slices by at least half. Brush with oil, sprinkle with 1 tsp. chopped rosemary and one third minced garlic, and season with salt and pepper (if desired). Spread 1 cup Swiss chard over potatoes, sprinkle with 1/4 cup chopped onion and one third crumbled Taleggio. Arrange another layer of sweet potatoes over chard, and press down on potatoes to flatten layers. Repeat layering twice.

Place torte on baking sheet, and cover with foil. Bake 45 minutes. Uncover, and bake 15 minutes. Cool 15 minutes. Press top of torte to remove excess liquid.

Turn torte upside down on platter, unmold, and serve. For a crispier top, unmold onto ovenproof platter, and brush top of torte with oil. Broil 3 to 5 minutes, or until potato slices begin to brown and start to curl. Cool 10 minutes before slicing.