Ingredients
4 large egg yolks
2 tablespoons apple-cider vinegar
1 teaspoon sugar
2 teaspoons Dijon mustard
3 tablespoons olive oil
1/2 cup milk
1 tablespoon cornstarch
Coarse salt and freshly ground pepper
Preparation
Mix all ingredients in a medium heatproof bowl. Set it over a pot of simmering water. Cook, stirring constantly, until the sauce thickens slightly, 5 to 7 minutes. A finger drawn across the back of the spoon should leave a trail. Do not overcook the sauce since it will curdle. Taste and adjust the seasoning. Sauce can be kept warm over a pan of hot water, but should be used as soon as possible.
