Slit the mentaiko sacs lengthwise and carefully scrape out the roe into a medium mixing bowl.
2
To the bowl with mentaiko, add the heavy cream, unsalted butter, koikuchi soy sauce, mirin, and dashi stock. Whisk vigorously until all ingredients are well combined and the sauce is smooth.
3
Bring a large pot of water to a rolling boil. Add the Udon noodles and cook according to package instructions until they are al dente. Drain the Udon noodles thoroughly.
