Remove plastic wrap from frozen udon and place it on a microwave safe bowl
Place butter on the udon
Microwave for 2-3 min until the udon is hot
Mix udon until it is evenly coated in the melted butter
Add thinly sliced nori and chopped green onions
Remove membrane or sack from mentaiko or pollock roe
Place mentaiko on udon
Add egg
Pour a dash of mentsuyu over udon to your liking (about 1-2 tbsp) since the mentaiko is flavorful and salty as well.
Mix well before eating and enjoy