1 tablespoon oil
2 large garlic cloves, minced
2 large onions, sliced thin
2 white turnips, sliced thin
2 yellow turnips, sliced thin
2 large potatoes, peeled and sliced
2 sweet potatoes, peeled and sliced
1 cup water
1 cup stock, chicken or vegetable (plus additional stock for pureeing)
Heavy cream (optional)
Salt and freshly ground pepper