Preheat oven to 220 deg Celsius. Line a baking tray with non-stick paper.
Sift the flour, baking powder and salt into a bowl. Rub in the margarine until the mix resembles breadcrumbs.
Fold in the dry mustard, cheese and pineapple. Add enough milk to make a fairly soft dough.
Lightly flour your surface. Turn out your dough and knead lightly. Gently roll out to 2cm (3/4") thickness. Be careful not to overwork. Using a 5cm cutter or glass, stamp out rounds (using even pressure). Move them to the prepared tray.
Brush tops with milk and bake for about 10 minutes, or until well risen and golden. Cool on wire rack before serving either warm or cold.