To make the sauce, first chop the onion roughly. Then chop the red and yellow peppers into squares.
Heat the oil in a wok or a large frying pan over medium-high heat. Stir-fry the onion and bell peppers for 4 minutes, or until they begin to soften.
Add the ginger and cook for 1 minute, then add the broth, soy sauce, sugar, vinegar, tomato paste, and canned pineapple with its juice.
Bring to a boil and simmer for 1 minute, then add corn starch mixture, and simmer for another 2 to 3 minutes, stirring until thickened. Keep the sauce warm over very low heat while you cook the pork.
Whisk the egg yolk, corn starch, salt, and milk together. Add the pork and mix until covered.
Heat the canola oil and fry the pork over medium heat for 3 to 4 minutes, until it's golden on the outside and cooked completely through. You may need to cook the pork in batches so you don't overcrowd the pan. Mix the cooked pork with the sauce.