1. Prepare ample boiling water. Pick beef with chopsticks and boil. Do it on your own way and drain on paper towel.

2. Arrange on a plate. Garnish with roughly torn shiso leaves and serve with gomasu.

For how long you should cook with your microwave oven, see Cooking Time vs Wattage Conversion.
For more tips of using Microwave Oven, see Sachiko's Guideline to Microwave Cooking.