Simmer: Heat the broth in a large saucepan and keep at a simmer.
Toast: In another large saucepan, over medium-low heat, melt butter. Add onion and cook until soft, about 5 minutes. Stir in the rice and toast, about 3 minutes.
Stir: Increase heat to medium. Pour in wine; stir until absorbed. Scoop in the hot broth, one cup at a time, stirring until each dose has been absorbed. When half the broth remains, add the peas.
Season: After about 20 minutes, when most of the liquid has been added and the rice tastes delicious, but firm, turn off the heat. (You may not need all the broth.) Stir in the cheese, zest, mint and cream.