1 large egg yolk, at room temperature
1 tablespoon rice vinegar
1 teaspoon dijon mustard
1 teaspoon granulated sugar
1/4 teaspoon salt
1 cup neutral-flavoured oil (e.g., vegetable or canola oil)
1/4 teaspoon MSG (monosodium glutamate) optional, but it mimics the umami flavour found in commercial Japanese mayo