Dietary guidance: v v
handful of mushrooms
a tin of chunked pineapple in its own juice. not syrup. never syrup.
bottle of soy sauce (you won't use it all)
any vegetables really
(any meat if you want it)
Chop up the vegetables (and meat if you want it)
You want it all sliced thin so they'll cook quickly
Put a tablespoon of cornflour in a mug. Add the pineapple juice and stir. You do NOT want big lumps. Cornflour and juice is a "Newtonian" liquid... which means it's half liquid half solid and if you BASH it suddenly it becomes a solid. This is bad news as far as lumps are concerned.
Add soy sauce, you'll need about a dessert spoon. The sauce won't look all that great but it will taste terrific.
Fry the veggies and pineapple together on a hot heat. Pour the sauce over the top. Serve immediately.