In a medium size saucepan, melt butter over medium heat. Add onions cooking until translucent, about 2 minutes, Add flour, stirring until absorbed.
Gradually whisk in half and half. Bring to a gentle boil then add salt, black pepper, garlic, onion powder and nutmeg. Add peas, mix until coated with sauce.
Cook over medium heat for 5-7 minutes or just until peas are tender. Stir occasionally.