Homemade Kewpie Mayonnaise

Makes about 1 cup 

2	 tablespoons plus 1 teaspoon cider vinegar 
2	 tablespoons dashi, homemade or instant (optional) 
1	 teaspoon Dijon mustard 
1	 egg yolk 
3/4	 cup canola oil 
1/2	 teaspoon sugar 
1	 teaspoon kosher salt 

1 In a small saucepan, bring the the cider vinegar and dashi to a simmer over high heat (if you aren't using dashi, just simmer the vinegar). Adjust the heat to keep it simmering, not boiling, until reduced to about 1 tablespoon, 3 to 5 minutes. 
2 Transfer the vinegar-dashi concentrate to a small mixing bowl. Form a ring with a damp dish towel to rest your bowl on—this will keep it stable. Add the Dijon and egg yolk and whisk to combine. 
3 While constantly whisking, very gradually drip in the oil down the side of the bowl into the yolk mixture. The mixture should emulsify and thicken.* You can drizzle a bit more quickly once the mixture is very thick. 
4 When all the oil has been incorporated, mix in the sugar and salt. You can add a little dashi or water to thin the mayonnaise so it will easily flow from a squeeze bottle but still hold its shape. It will thicken slightly once refrigerated. Transfer the mixture to a squeeze bottle. Refrigerate and use within 1 week. 
5 *If at any point you mixture breaks and separates instead of getting thick and creamy, don’t despair. Put a fresh egg yolk in a bowl, and slowly whisk the broken mixture into it, as if it were the oil: https://food52.com/blog/3711-how-to-fix-broken-aioli

https://food52.com/recipes/39834-homemade-kewpie-mayonnaise