01 - Place halved potatoes in large saucepan, cover with cold salted water, bring to boil over medium-high heat, reduce heat and simmer 12–15 minutes until fork-tender.
02 - Add peas to pot during last 3 minutes of potato cooking time, drain and set aside.
03 - Melt butter in large skillet over medium heat, whisk in flour and cook stirring constantly 1–2 minutes to form roux.
04 - Gradually whisk in milk followed by heavy cream, stirring until smooth and thickened 3–5 minutes.
05 - Season sauce with salt, pepper, and nutmeg if desired.
06 - Add drained potatoes and peas to sauce, gently fold to coat evenly, cook 2 minutes to heat through.
07 - Transfer to serving bowl and garnish with fresh parsley.