In a pot, sauté onions and garlic in a mix of butter and oil. Cook until the onions are translucent and soft but not brown.
Add the rice and let it sauté until it starts to absorb the fat. Then add the white wine and let it evaporate.
Add the boiling stock a little at a time, and let it almost evaporate before adding more. Stir the risotto almost continuously throughout.
After approximately 20 minutes, the rice should be tender. It should not be as soft as rice pudding but still have a slight bite. The risotto should not be dry, but rather a bit fluid.
Remove the pot from the heat and stir in parmesan and extra butter. Season with salt, pepper, and white wine vinegar and serve immediately.
Serve the risotto with crispy fried Serrano ham and avocado.