Place the pineapple in a colander set over a large bowl. Drain pineapple thoroughly, pressing on it with the back of a spatula until no more juice comes out. This is essential to not having a watery salad, so please drain it really well!
Chop the apples into ½ inch pieces. Place the apples in the bowl with the pineapple juice and toss. Let sit while you prepare the rest of the salad.
In another large bowl, whisk together the egg, flour, and vinegar until smooth. Whisk in the sugar.
Reserve 2 tablespoons of nuts to sprinkle on top.
Using a spatula, fold in the drained pineapple, the rest of the nuts, and whipped topping.
Drain the apples and place them on a clean kitchen towel. Use the towel to thoroughly dry the apples. This is also essential to not having a watery salad!
Fold in the apples with a spatula. Transfer to a serving bowl, and top with the reserved nuts.
Serve immediately, or refrigerate until ready to serve.