1.Beat butter, sugar and egg in a small bowl with an electric mixer until combined. Transfer to a medium bowl, stir in sifted flours and cocoa, in two batches.
2.Knead dough on a lightly floured surface until smooth. Roll between sheets of baking paper until 3mm (¼-inch) thick. Wrap in plastic wrap, refrigerate 30 minutes.
3.Preheat oven to 180°C (160°C fan forced). Grease two oven trays, line with baking paper.
4.Using a cutter, cut 28 rounds from the dough, place 3cm (1¼-inches) apart on trays. Bake 12 minutes or until firm. Cool on wire racks.
5.Place half the biscuits, base-side up, on an oven tray. Using scissors, cut 28 marshmallows in half horizontally. Press four marshmallow halves, cut-side down, onto each biscuit base on the tray. Bake 2 minutes.
6.Meanwhile, spread ½ teaspoon of jam over bases of remaining biscuits, press immediately onto the top of the softened marshmallow. Stand 20 minutes or until marshmallow is firm.
7.Melt chocolate in a medium heatproof bowl over a medium saucepan of simmering water (don’t let water touch base of bowl). Remove from heat, stir in oil. Hold mallow wheels on their side, dip into chocolate, spinning around like a wheel to cover side, then place on a wire rack. Spoon more chocolate over the top and use a metal spatula to smooth. Remove excess chocolate using the spatula. Stand until set, then turn over and cover the base with chocolate. Stand biscuits on a baking-paper-lined tray until chocolate sets.
You need a 7cm (3-inch) round fluted cutter. Dutch cocoa is cocoa powder that has had an alkaline added, giving it a rich colour and deep full chocolate flavour. It is available from major supermarkets.Note