Cut fennel stalks and fronds from the bulbs. Wrap stalks and fronds in a damp paper towel and store in the refrigerator. Quarter fennel bulbs then place in a large, airtight jar. Add the vodka, seal the jar and let steep for 5 days in a cool, dark spot. On day 3, take the stalks and fronds the refrigerator. Trim fronds from the stalks and add to the jar with vodka and bulbs. Discard stalks. Reseal the jar and shake.*