MIX together the stock, soy sauce, oyster sauce, sesame oil and black pepper in a small bowl. MIX 1 tablespoon of cornstarch to a paste with 1 tablespoon water in another small bowl. CUT the block of tofu into 3 square slices (roughly half an inch thick). PAT the tofu slices dry with paper towels. CUT the slices diagonally from corner to corner to make 4 triangles per slice. PUT a thin layer of cornstarch on a plate. Dip the tofu triangles into the cornstarch, coating the pieces lightly all over. HEAT 2 tablespoons of the oil in a large skillet or frying pan over a medium-high heat. ADD the tofu triangles and pan-fry for around 5-6 minutes on each side, or until crisp and golden. WHILE the tofu is cooking heat a wok or large skillet over a high heat then add 1 tablespoon of oil. STIR-FRY the broccoli and red pepper for 4 minutes. ADD the scallion and garlic and stir-fry for 1 minute. ADD the sauce mixture and stir-fry 15 seconds until thoroughly coated, then stir in the cornstarch paste and cook until thickened. ADD the crispy-fried tofu and toss to coat with the sauce. SERVE immediately with rice or noodles.