Warm your pan over medium heat and melt the butter or swirl in olive oil. You want a glossy, not a smoky affair.
Add garlic if using and sauté 30 seconds until fragrant. Don’t burn it—garlic bitterness is a vibe killer here.
Stir in the sour cream and milk/broth. Whisk until smooth and creamy. Yes, whisk like you mean it.
Drop in Dijon mustard and sugar. Taste and tweak until it’s bright but not off-puttingly sweet.
Fold in chopped chives or parsley. Season with salt and pepper to your liking. Simmer 1–2 minutes to meld flavors.
If the sauce gets too thick, splash more milk or stock a little at a time. If it’s too thin, simmer a bit longer while whisking.
