For the dipping sauce, combine water, sugar, vinegar and salt in a medium-sized pot over medium heat. Bring to a gentle simmer and stir occasionally for 15 minutes until the sauce begins to show signs of thickening/turning glossy. Pour into a bowl to one side to cool for 10 minutes, then stir in the chilli, shallot and cucumber and rest until ready to serve.
Meanwhile, use a pestle and mortar to crush the garlic, white pepper and coriander roots into a paste. Alternatively, you can use a knife to very finely dice the garlic and coriander root then use the side of the knife to mash into a paste as best you can. Add to a bowl with the pork, oyster sauce, sugar and 2 tsp soy sauce. Use a fork or your hand to combine until everything is evenly distributed then leave to marinate for 10 minutes. Add in 1 egg and use a fork to combine with the pork.
Cut each slice of bread into 4 pieces, resulting in 20 pieces total. Use a knife to spread the pork over each slice of bread, then press in a chilli slice and coriander leaf into each piece. In a bowl, whisk 2 eggs and 1 tsp soy sauce.
Heat up at least 1/2 inch of oil in a large deep pan over medium heat until it reaches 170C/340F. Take a piece of bread, dunk it meat-side-down into the egg wash and add it to the oil meat-side-down. Quickly repeat with 4 more pieces. Leave to fry for 2 minutes, then flip and fry for another 2 minutes, or until deep golden and crisp with the pork piping hot. Remove the pieces and place them on a wire rack above a tray to catch any excess oil. Repeat with the remaining batches.
Serve with the dipping sauce then tuck in and enjoy!