definitely doable. You have to use hardneck garlic. The hardiest
varieties overwinter in Zone 2. Try Territorial Seeds for varieties
named Tundra or some other suggestive name (I have two of them, one is
Siberian and the other is the one they claim to be cold-hardiest).
Follow the instructions of Bear, though in Zone 5 I pick in early
august. the onions will be trickier as they are not as cold hardy. Pile
the mulch, and onions want more lime and more nitrogen during growth
than garlic, which only needs a bit of nitrogen.