Wash and clean the potatoes. Halve them (lengthwise) and brush the cut surfaces with olive oil. Lightly salt the potatoes and scatter some coriander on them.
Place the cut sides on to an greased baking tray and bake the potatoes for about 10 minutes (at 220°C). Then bake again for 15 minutes (at 150°C).
Heat up the Gyros in a pot. Peel the garlic cloves and chop finely. Fold into the Gyros together with the mustard.
Hollow out the tomatoes and fill with the hot Gyros. Before serving, place one filled tomato in the middle of the plate with two potato halves. Garnish with soya yoghurt, lemon strips and chives.