Preheat oven to 180°C and line two baking trays with baking paper.
Place margarine and sugar in a mixing bowl and beat with an electric mixer until light and creamy.
Add remaining biscuit ingredients and beat until combined, then use your hands to work into a dough. Form a ball and cover with plastic wrap. Refrigerate for 30 minutes.
Roll heaped tablespoons of biscuit batter in your hands to form a ball. Place on lined baking trays and press down gently with your fingers to flatten.
Bake for 15 minutes or until just golden. Remove from oven and cool on tray for 5 minutes before transferring to a wire rack to cool.
Spread jam over the cooling biscuits, then place a marshmallow half on top.
Melt chocolate in the microwave. Drizzle over marshmallow and biscuit until fully coated. Place on wire rack until chocolate has set.