Core the cabbage and blanch in salted boiling water 10 minutes. Let cool and separate the leaves.
In a bowl, combine salt, onions, garlic, lamb, rice, egg, lemon juice and thyme. Divide the filling between the cabbage leaves and roll up, tucking in the ends.
Slice any remaining cabbage leaves. Heat vegetable oil in a saucepan and lightly fry the cabbage rolls. Add cabbage strips, bay leaf, vegetable stock and rosemary. Cover and simmer on low heat for 50 minutes.
Remove the cabbage rolls and add the flour and creme fraiche to the saucepan, stirring well. Bring to a boil, then return the cabbage rolls to the saucepan and serve.