1 large egg yolk
1 tablespoon rice vinegar
1 teaspoon Dijon mustard
1 teaspoon sugar
1/2 teaspoon salt
1 cup neutral oil
Optional: 1 teaspoon lemon juice
Whisk egg yolk, vinegar, mustard, sugar, and salt until combined
Very slowly drizzle in the oil while whisking constantly
Continue whisking until thick and creamy
Adjust salt, sugar, or vinegar to taste
Chill before using