Heat oil in a large nonstick skillet over medium heat. Add fennel seeds, ginger, star anise, and garlic to pan; cook 2 minutes, stirring occasionally. Add sliced fennel to pan; cook 5 minutes or until lightly browned, stirring occasionally. Add vinegar, scraping pan to loosen browned bits. Stir in syrup, salt, and pepper; bring to a simmer. Cook 15 minutes or until fennel is tender. Discard anise.