Beef Griddle with Onion Rings (Oil-yaki)

This is traditionally cooked on a lightly oiled hot-plate at the table. Since I don't know anyone who has that facility, I've given the Westernised version below.

Serves 4

450g sirloin or topside beef, in one piece
2 Spanish onions, cut into thin rings
75g watercress sprigs
1 lemon, quartered
vegetable oil
10cm piece large daikon (white radish), peeled & grated
shoyu

Trim any fat from beef, then cut piece lengthways in half.
Freeze two pieces separately in freezer bags for at least 2 hours or overnight.
Part thaw frozen beef for about 30 min, or until outside just begins to soften.
Then cut each piece of beef across into slices, as thinly as you can.
Pan-fry beef & onions in a little oil & divide between 4 plates.
Garnish with lemon wedge & watercress & serve immediately, with daikon & jug of shoyu.
Diners mix their own dipping sauce made from daikon, lemon juice & shoyu.
Can be accompanied by steamed rice as well.