First you need to press any excess liquid out of the tofu. If you have a tofu press, use that - or if not, cut the tofu into 4 even slices, and lay it out on a clean tea towel. Lay another clean tea towel over the top, add a baking tray, and then place a large pan full of water on top. The weight of the water will press out any excess liquid from the tofu into the tea towels. Leave for 10 minutes or so.
Meanwhile, prepare the coating. To make the batter, combine the plain flour, spices, and plenty of salt and pepper in a mixing bowl. Add the water, and mix with a fork to give a fairly thick batter. You can adjust the consistency by adding a dash more water or a little more flour if needed - you want it to be just too thick to pour, but still fairly loose.
In a separate mixing bowl, crush the corn flakes into a coarse crumb.
Lightly grease a baking tray.
When the tofu has been pressed, cut it into nugget shapes (I ended up with 8 large nuggets, but you could make 16 small ones if you prefer). With one hand, coat each nugget in the batter, being sure to cover all sides, and allow any excess batter to fall off into the bowl. Drop the battered nugget into the other bowl, and use your other hand to coat it in the crushed corn flakes. Place it on the baking tray, and repeat with the remaining nuggets. Spray them lightly with oil.
Bake the tofu nuggets at 190°C (Gas Mark 5 / 375°F) for about 30 minutes, or until crispy. Serve immediately (they're best eaten fresh!).