Boil the udon noodles in boiling water, then drain in a strainer.
Melt butter in a pan and sauté minced garlic.
Add onion and sauté until it becomes translucent.
Pour in the heavy cream and milk, and bring to a gentle boil.
Add Parmesan cheese and mix until the sauce thickens, then add the udon noodles and toss together.
Season with salt and pepper to taste.
Serve on a plate and top with flying fish roe, chopped scallions, and shredded seaweed to finish.