Boil 3/4 pound sugar snap peas in salted water, 3 minutes. Add 2 bunches thinly sliced baby turnips; cook 2 minutes, then drain. Cook 1 sliced onion and 1 chopped garlic clove in butter until soft. Add the vegetables, 1 tablespoon sugar, and salt and pepper; cook until glazed. Top with chopped parsley. Serve with lemon wedges.