Preheat oven to 350°F. Line an 8" x 8" baking pan with parchment paper in both directions, leaving overhang on each side (to grip later). Drain pineapple well through a strainer; press down to release juice. Set pineapple aside in the fridge. Discard juice or reserve for another use.
Melt butter in a microwave-safe bowl (1 minute or so). Stir in graham crumbs; mix well. Press into bottom of prepared pan. Bake for 8-10 minutes until lightly browned. Chill.

Make icing: Beat butter with vanilla, salt and 1 tbsp of the milk. Slowly beat in the icing sugar until the mixture comes together smooth and fluffy. Add as much of the remaining milk as needed to maintain smooth consistency. With an offset spatula, spread a thin layer over the cooled crumb base and chill.

Filling: Mix the chilled, drained pineapple with the chilled, shaken cream. Spread over the icing layer. Sprinkle with last 1/4 cup of the graham crumbs and chill. Lift out and cut into desired-size portions. You can serve this as dessert by cutting into 9 squares (3 cuts across and 3 down) or into 16 cookies by making 4 cuts across and 4 down.