Japanese Mayonnaise (Kewpie-Style)

Ensure your egg yolks are at room temperature — cold yolks resist emulsification and will break more easily when the oil is added. Place the yolks in a medium bowl set on a damp cloth to prevent it sliding. Add the rice vinegar, Dijon mustard, MSG, and salt. Whisk vigorously for 60 seconds until the mixture is pale, slightly thickened, and completely homogenous. The mustard is not just for flavor — it contains lecithin, a natural emulsifier that reinforces the lecithin already in the yolks and gives you more leeway when adding the oil. The preliminary whisking begins to form the emulsion matrix before any oil is added.

The oil addition is the critical step: the first 25% of the oil must go in extremely slowly or the emulsion will break. Begin by adding the oil drop by drop — literally one drop at a time — while whisking constantly. Continue drop by drop for the first 50–75 ml of oil. As the emulsion establishes and the mixture visibly thickens and turns paler, you can increase to a very thin, steady stream. Once you have added half the oil and the mayonnaise looks thick and stable, you can add the remaining oil in a thin but steady stream, whisking continuously. If at any point the mixture looks glossy, greasy, or starts to pool with oil rather than incorporating, stop adding oil and whisk vigorously for 30 seconds before continuing. If you have a stand mixer or immersion blender, you can add the oil in a thin stream while the machine runs — the constant agitation is equivalent to whisking.

Stir in the dashi (if using) — add it a teaspoon at a time, tasting after each addition. The dashi adds a subtle background umami that rounds and deepens the flavor, characteristic of the complexity that makes Kewpie-style mayo so compelling. Taste the finished mayo carefully: it should be rich and deeply savory, with a bright, mild acidity from the rice vinegar (noticeably gentler than Western mayonnaise), and a longer umami finish from the MSG. Adjust with more salt, rice vinegar, or MSG as needed. Transfer to a clean, airtight jar. Japanese-style mayo keeps refrigerated for up to 2 weeks. It can also be transferred to a squeeze bottle for the distinctive Kewpie serving style.