Strain the juice from the canned pineapple into a small saucepan and set aside the crushed pineapple for later. Add the sugar and cornstarch to the saucepan.
Cook over medium-low, whisking often, for about 10 minutes until slightly thickened (it will foam a little). Stir in the crushed pineapple and cook for another 10 minutes.
Remove from the heat and allow to cool to room temperature. Store in an airtight container for up to 2 weeks.
Strawberry Sauce
Whisk together the cornstarch and warm water in a small saucepan. Add the strawberries and sugar.
Cook for 10-15 minutes over medium heat, stirring frequently, pressing down on the strawberries as they cook to break them up.
Remove from the heat and allow to cool to room temperature. Store in an airtight container for up to 2 weeks.
Banana Split
Peel the banana and cut it in half lengthwise. Place in a banana split dish. Place 2 scoops of each ice cream flavor (see note) side by side between the banana slices.
Add the pineapple sauce over the vanilla ice cream, strawberry sauce over the strawberry ice cream, and chocolate sauce over the chocolate ice cream.
Add a dollop of whipped cream on top of each ice cream flavor, top each dollop with a cherry, and then sprinkle with chopped peanuts. Serve immediately.
Notes
I use 2 small scoops of each ice cream flavor to make our banana splits. You can use 1 medium to large scoop of each flavor if you prefer.