In a separate bowl, whisk together the sesame paste, sugar, vinegar, sesame oil, dark soy sauce and salt until there are no lumps (it’s OK if it’s a little grainy at this stage). Add the water and whisk again to blend. The mixture should start looking glossy. Finally, add the honey and wasabi paste and whisk until the sauce is smooth, shiny and coats the back of a spoon. Taste and correct the seasoning if needed: The sauce should be well-balanced between sweet, nutty, umami and tangy notes, ending with a mustardy kick. The mouthfeel should be rich and silky.