Ingredients :

• Hard-boiled egg yolk — This is what gives the color and the creamy base. Hard-boiled, it mashes into a fine, dry paste that absorbs everything else. A soft-boiled egg wouldn’t work — too wet, the texture would turn watery. Five minutes in boiling water is enough.
• Fromage blanc 0 % — The real secret of the recipe. It replaces the oil and brings that characteristic melt-in-the-mouth quality without the richness. Use it very cold, straight from the fridge at the last moment — the sauce will be firmer and more pleasant to work with. No plain yogurt instead: the texture is too liquid and too acidic.
• Mustard — One tablespoon, no more. It plays two roles: the signature mayo taste and a slight binding effect. Classic Dijon mustard, not whole grain here — the grains would break the smooth texture we’re looking for.
• Lemon juice — 60 ml is almost half of a medium lemon. Squeeze it fresh — bottled lemon has that flat, metallic acidity that distorts the sauce. It’s what lightens everything up and gives it that zing that keeps you coming back for a second spoonful.