01 -
Melt the butter with the olive oil in a large heavy-bottomed skillet over medium heat. Add the thinly sliced onions and cook, stirring frequently, until the onions are golden and caramelized, about 20 minutes.
02 -
Stir in the minced garlic and cook for 1 minute, ensuring the garlic remains fragrant and does not burn. Add the Arborio rice, stirring to coat the grains with the butter and oil. Toast for 2–3 minutes until the edges of the rice become translucent.
03 -
Pour in the dry white wine, scraping up any browned bits from the bottom of the pan. Allow the wine to simmer until it is almost completely absorbed by the rice.
04 -
Reduce the heat to medium-low. Add the chicken stock one ladleful at a time while stirring continuously, allowing each addition to be absorbed before the next. Continue until all the stock is incorporated and the rice is creamy and al dente, about 18 minutes.
05 -
Fold in the grated Parmesan cheese and mascarpone cheese. Stir until both are fully melted and the risotto is creamy. Season to taste with kosher salt and freshly ground black pepper.
06 -
Spoon the risotto into warm bowls and garnish each portion with fresh thyme sprigs.