Peel and finely chop the onion. Heat oil in a pot, fry onion over low heat until transparent. Add rice and sauté briefly. Gradually add 800 ml broth and wine, stirring from time to time.
Always add the next portion of liquid only after the rice has absorbed the liquid. Cook for a total of 25-30 minutes. Stir in Parmesan cheese shortly before the end of cooking time. In the meantime, place the vegetables in a hot, coated pan without defrosting them.
Fry the vegetables for about 4 minutes at high heat, then continue to fry for about 5 minutes at reduced heat, stirring occasionally. Fold the vegetables into the finished risotto. Season to taste with salt and pepper.
Fill salmon slices with vegetable risotto. Keep the rest of the vegetable risotto warm and serve it later with the rolls. Spread the crème fraîche on the bottom of a greased casserole dish. Place the salmon rolls on top and bake in a preheated oven (electric range: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 5 minutes.
Garnish with chives.