In a saucepan, soften the onion and garlic in the oil. Add the rice and cook for 1 minute, stirring to coat thoroughly. Deglaze with the wine and reduce until almost dry.
Add the lobster stock, 250 ml (1 cup) at a time, stirring frequently until the liquid has been completely absorbed before adding more liquid. Season with salt and pepper. After 20 to 25 minutes, the rice should be al dente.
Stir in the peas and cook for about 1 minute. Add the lobster meat and mascarpone and heat through while stirring. Adjust the seasoning. Serve drizzled with lobster oil, if desired.
If using fresh peas, add them about 5 minutes before the end of cooking.