Combine the onion, garlic, and flour in a saucepan and cook over medium heat for 2 minutes.
Add the vegetable broth, milk, salt, pepper, and lemon juice. Bring to a boil and heat for 8 to 10 minutes over medium heat or until the sauce is creamy.
Pour this mixture into your blender and add the nutritional yeast. Blend until a smooth sauce is obtained. Adjust seasonings to taste.
Pour the sauce back into the saucepan and add peas. Warm the sauce for few minutes.