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.
Serve immediately.
Notes
Peas: You can use canned peas only in a pinch, but frozen peas will give you the best and tastiest end result. Canned peas can turn out a bit mushy. It's not necessary to thaw the peas prior to adding them to the cream sauce.
Half and Half: I prefer half and half for making these creamed peas, but you could adapt using whole milk or heavy cream, if that's what you've got on hand. To make your own half and half, use equal parts milk and heavy cream and you'll be good to go.
Seasonings: Nutmeg is typically added to a homemade bechamel sauce and I love including a pinch or two in this recipe. It's optional, and you could choose to omit but it adds a depth of flavor to the sauce that complements the peas.
Mushrooms: You could saute mushrooms with the onion, cooking until they're softened and the liquid has been released.
Fresh Herbs: You could add fresh chives, basil, parsley or thyme to the cream sauce.
Don't Thin the Sauce Too Much: If the cream sauce seems thick when first adding the peas, don't be tempted to add more liquid. It will thin a bit as they thaw and release liquid into the sauce.
Onion: You could add one cup of frozen pearl onions to the peas in place of diced onion. Add them to the saucepan with the peas, cooking until thawed and heated through.