1. Rinse and drain collards. Trim and discard tough stems. Stack collard leaves and slice thinly crosswise.
2. In a 10- to 12-inch nonstick frying pan over high heat, stir bacon and onion until bacon is crisp and onion is lightly browned, about 15 minutes. Pour half the mixture (with drippings) into a bowl.
3. Add manioc and butter to pan. Stir often until manioc is golden and crisp (bite to test), 4 to 6 minutes. Pour into a bowl at once. Serve hot, warm, or at room temperature, topped with olives.
4. Return remaining bacon-onion mixture to pan. Stir in about half the collards until wilted, 1 to 2 minutes. Add remaining collards and stir until all are wilted, 1 to 2 minutes more.