In a Saucepan over medium/high heat add olive oil and warm, add onions and garlic and sauté until onions are soft.
Add white wine and bring up to a boil, stir in mascarpone, cream. Stir constantly until cheese is completely melted.
In a greased oven safe pan add potatoes, grated cheese and pour sauce over potato mixture.
Place in a preheated 350°C oven and bake uncovered for 30 minutes.