Preheat oven to 225 degrees F.
Combine oil, 20 star anise, cardamom, nutmeg, and fennel in a saucepan.
Bring just to a boil. Cover and place in oven for 2 hours. Remove from oven and cool.
Strain into a bottle. Add 10 star anise and green peppercorns.
Cap and refrigerate. Use within 5 days.
Makes 4 cups.