Preheat an oven to 200ºC. Grease a baking tray with a little oil. Place whole wheat flour in a large bowl. Add butter, four tablespoons water and mix well.
Knead into a soft dough. Cover and set aside to chill in the refrigerator for half an hour. To make the filling, heat oil in a deep non-stick pan, add mustard seeds and let them splutter. Add potato, carrot, radish, onion and garlic.
Mix well and sauté, stirring occasionally, for two minutes. Add curry powder, turmeric powder and cumin powder mustard seeds and mix well. Cook, stirring continuously, for one minute.
Add vegetable stock, mix and bring it to a boil. Cover and simmer, stirring occasionally, till vegetables are tender. Set aside to cool. Divide the dough into equal portions. Roll each portion into a six inch round. Place some filling on one half of each round. Brush the edges of each round with soya milk.
Fold over and press the edges together to seal. Arrange on the baking tray. Bake in the preheated oven for twenty-five to thirty minutes or until golden brown. Serve hot.