Preheat the oven to 180 ° C.
Peel the turnips then cut them into thin slices. Cook in boiling water for 10 to 15 minutes or 3 minutes under pressure. The slices should not be too tender otherwise they will mash.
In a frying pan, brown the onions and bacon in a little oil. Deglaze with white wine then simmer for a few minutes while the alcohol evaporates.
Add the sour cream, salt and pepper and simmer for a few minutes.
In an oven dish, place the slices of turnips with the cream, bacon and onion mixture. Mix together.
Place the cheese cut in half lengthwise on top.
Bake for 40 minutes at 180 ° C.