Sprinkle the yeast over warm water in a large bowl. Let stand for 5 minutes until the yeast softens and begins to form a creamy foam. Beat in the sugar, egg, 1/2 teaspoon salt and wholemeal flour with an electric mixer on low for 3 minutes. Stir in the bread flour, 60g at a time, mixing well after each addition. When the dough has pulled together, turn it out onto a lightly floured surface and knead until smooth and elastic, about 8 minutes. Lightly oil a large bowl, then place the dough in the bowl and turn to coat with oil. Cover with a light cloth and let rise in a warm place (27 to 35 degrees C) until doubled in volume, about 30 minutes.
While the dough is rising, heat a large frying pan over medium heat and cook and stir until the pork is crumbly, evenly browned and no longer pink. Drain and discard any excess fat. Stir in the ranch dressing mix until meat is well-coated. Add the cabbage, courgette, onion, red pepper, carrot and garlic. Cook and stir until the vegetables are tender and most of the liquid has evaporated, about 10 minutes. Season with salt and pepper. Set aside.
Deflate the dough and turn it out onto a lightly floured surface. Use a knife to divide the dough into four equal pieces - don't tear it. Roll each portion out to an 20cm square, then cut each large square into four smaller squares. Place about 3 tablespoonfuls of the pork filling into the centre of each square. Bring the corners over the filling and pinch to seal. Secure with a cocktail stick if needed. Spray a baking tray with cooking oil spray. Place the pouches on the prepared baking tray about 7.5cm apart. Cover the buns with a damp cloth and let rise in a warm place until doubled in volume, about 30 minutes.
Preheat oven to 180 C / Gas 4.
Bake in the preheated oven until golden brown, about 15 minutes. Remove from tray and discard cocktail sticks. Brush each pocket with melted butter. Serve hot.