Warm the broth in a saucepan over low heat and keep it warm throughout cooking.
Heat a wide skillet or pot over medium heat and add the olive oil and 1 tablespoon of butter.
Add the diced onion and cook for 4 to 5 minutes, stirring often, until soft and translucent.
Add the minced garlic and cook for 30 seconds, stirring constantly.
Stir in the Arborio rice and cook for 1 to 2 minutes until the grains are coated and lightly toasted.
Pour in the white wine and stir until mostly absorbed, about 2 to 3 minutes.
Add 1/2 cup of warm broth and stir until the liquid is mostly absorbed.
Continue adding broth 1/2 cup at a time, stirring frequently and allowing each addition to absorb before adding more, for 18 to 22 minutes total.
When the rice is tender with a slight bite, stir in the peas and cook for 2 to 3 minutes until heated through.
Turn off the heat and add the remaining 1 tablespoon of butter, the Parmesan cheese, the lemon zest, and 1 tablespoon of lemon juice.
Stir until the risotto is creamy and glossy.
Add the chopped herbs or heavy cream if using and stir to combine.
Taste and adjust salt, pepper, and lemon juice as needed.
Add a splash of warm broth if the risotto thickens too much before serving.