Prep your ingredients. Zest one lemon, then juice it to get about 2–3 tablespoons. Cut the butter into small cubes and keep it cold. Mince the shallot and garlic.

Gently sauté aromatics. In a small saucepan over medium-low heat, add a teaspoon of butter. Cook the shallot with a pinch of salt for 2–3 minutes until soft and translucent, not browned. Add the garlic and cook 30 seconds until fragrant.

Deglaze with wine or stock. Pour in the white wine (or stock). Increase heat to medium and simmer for 2–3 minutes, reducing the liquid by about half. This concentrates flavor and cooks off the raw taste.

Add lemon juice and zest. Stir in the lemon juice and a pinch of zest. Simmer 30–60 seconds to warm through.

Optionally add cream. Reduce the heat to low and whisk in the heavy cream. Let it come to a gentle simmer. This gives the sauce a cushion so the butter emulsifies more easily.

Emulsify with cold butter. With the heat on low, whisk in the cold butter a few cubes at a time. Let each addition melt and emulsify before adding more. Keep the sauce just warm—if it boils, it may separate.

Season to taste. Add salt and pepper. Adjust acidity with a splash more lemon juice if needed. If the sauce tastes flat, a pinch of salt usually fixes it; if it’s too sharp, whisk in another small cube of butter.

Finish and serve. Remove from heat. If you prefer a silky texture, strain out the shallots and garlic; otherwise, leave them in. Stir in parsley for color. Serve immediately over fish, chicken, pasta, or vegetables.