Combine 2 tablespoons of mentaiko, soy sauce, and mirin in a bowl. Mix together well and set aside.
In a pot with boiling water, cook the udon noodles according to the package instructions.
While the udon is cooking, heat a pan on the stovetop over medium heat. Melt butter and add grated garlic. Cook for about 1 minute until fragrant but not browned. Add heavy cream, gochujang, kewpie mayo and mix together well.
Toss in the cooked udon noodles, making sure the noodles are coated evenly with the sauce.
Transfer the udon to the mentaiko mixture from earlier and mix until fully combined.
Garnish with chopped scallions, nori strips and a dollop of roe.
