In a food processor, combine the flour, baking powder and salt. Add the green onions and pulse until finely chopped. Add the butter. Pulse until the butter forms pea-sized pieces. Add the milk and pulse until the dough begins to form. Remove and shape into a disc.
On a lightly floured surface, roll out the dough into a sheet 1/8 inch (3 mm) thick. Trim the edges to obtain an 11-inch (28 cm) square. Transfer to the prepared baking sheet and fold the edges to create a 1/2-inch (1.5 cm) border. Keep in the freezer while preparing the pork belly.
With the rack in the middle position, preheat the oven to 400°F (200°C).
In a large non-stick skillet over medium heat, brown the pork slices in the oil. Drain the oil and reposition the pork in the skillet. Add the onions overtop, cover and cook for 2 minutes. Add the maple syrup and soy sauce. Cover again and simmer for 10 minutes. Uncover and let the sauce reduce until almost dry, stirring halfway through cooking. Season with pepper and set the pork aside on a plate.
Spread the onions over the crust, then place the pork slices overtop. Bake for 25 minutes or until the crust is golden brown and the pork is caramelized.
Delicious with fennel and broccoli salad (see recipe).