1. Combine nimono-shouyu with katakuri-ko in an ovenproof bowl and add garlic. Put the beef in it and coat with the sauce. Cover the beef tightly with a sheet of waxed paper, put a small plate as a drop-lid. Cover with the edge-open wrap.

2. Microwave on 600W for 7minutes (3 and half minutes on 1200W).

3. Take out, turn over the beef and coat with the sauce. Put back the waxed paper and leave to cool.

4. When it is completely cool, slice into 2-3mm and garnish with watercress. Serve with mustard and strained sauce.

* Without using microwave, add 1/2cup water in a pot (Besides the ingredients). Turn around occasionally and simmer for 20minutes

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.