In a 5 Qt. Dutch oven over medium heat, combine onion and olive oil. Sweat the onions until they are translucent, about 4-5 minutes. Add garlic and cook until fragrant, 1 minute.
Add farro into the pot to toast, stirring frequently. 2 minutes
Add white wine and stir until most of the wine is evaporated. Add thyme sprigs.
Add ½- ¾ cup of stock to the pot, stirring frequently until the stock is mostly absorbed. Adjust heat as needed to keep the liquid at a simmer.
Continue stirring and adding ½-3/4 cup of stock at a time while stirring frequently until farro is cooked through. About 25 minutes. You may have a bit of leftover stock.
Once farro is cooked, remove the thyme stems. Stir in nutritional yeast, and remove from heat.
Add peas and arugula and stir allowing arugula to wilt and the peas to defrost.
Serve.