Cherry Marshmallow Swiss Roll

MAKE THE CHERRY COMPOTE (CAN BE DONE AHEAD):
1. Combine the quartered glacé cherries, chopped fresh or frozen cherries, sugar, lemon juice, and water in a small saucepan over medium heat.
2. Bring to a gentle simmer and cook for 8–10 minutes, stirring occasionally, until the fresh cherries have broken down and the mixture is thick and jammy. The glacé cherries should remain as distinct, jewel-like pieces throughout.
3. Remove from heat and let cool completely. The compote will continue to thicken as it cools. Refrigerate until needed. This can be made up to 3 days in advance.

MAKE THE DIGESTIVE BISCUIT SPONGE:
4. Preheat the oven to 200°C / 400°F. Line a 25 × 38cm (10 × 15-inch) jelly roll pan with parchment paper, leaving a slight overhang on the long sides. Lightly grease the parchment.
5. Crush the digestive biscuits to a fine powder using a food processor or a rolling pin and a sealed bag. No large pieces should remain — they would create weak points in the sponge where it could crack during rolling.
6. Whisk the flour, crushed biscuits, baking powder, and salt together in a bowl. Set aside.
7. In a large bowl or stand mixer with whisk attachment, beat the eggs and caster sugar on high speed for 5–7 minutes until the mixture is very thick, pale, and tripled in volume. When you lift the whisk, the batter should fall in a thick ribbon that holds its shape on the surface for 3–4 seconds before dissolving. This aeration is the single most important step for a Swiss roll that holds its round shape and does not sit down into an oval.
8. Add the vanilla and beat briefly to combine.
9. Fold in the dry ingredients in two additions, using a large metal spoon or flexible spatula. Work gently but confidently — cut down through the center, sweep along the bottom, and fold up and over. Rotate the bowl a quarter turn and repeat. Incorporate the flour mixture completely while deflating the batter as little as possible. The crushed digestive will absorb moisture faster than plain flour, so do not overwork the batter or it will become dense.
10. Fold in the melted butter by drizzling it down the side of the bowl and folding gently — no more than 5–6 strokes.
11. Pour immediately into the prepared pan and spread evenly using an offset spatula, working quickly. Pay special attention to the corners — thin spots will overbake and crack.
12. Bake for 10–12 minutes until the sponge is golden, springs back when lightly pressed, and has just begun to pull away from the edges. Do not overbake — an overbaked sponge will crack when rolled.

ROLL THE SPONGE:
13. While the sponge bakes, lay a clean, lint-free kitchen towel on the counter and dust it generously with caster sugar.
14. As soon as the sponge comes out of the oven, invert it onto the sugared towel. Peel off the parchment paper carefully.
15. Starting from a short end, roll the sponge up tightly together with the towel, creating a spiral with the towel trapped inside. This trains the sponge to hold its rolled shape. Rolling from the short end creates a taller, rounder roll with more visible spirals.
16. Place seam-side down on a wire rack and let cool completely, about 30 minutes. Do not rush this step; a warm sponge will melt the cream filling.

MAKE THE MARSHMALLOW CREAM FILLING:
17. If using mini marshmallows instead of fluff: place marshmallows in a microwave-safe bowl with 1 tablespoon of the cream. Microwave in 15-second bursts, stirring between each, until fully melted and smooth. Let cool to room temperature — the mixture must not be warm when folded into whipped cream.
18. Whip the heavy cream with the powdered sugar and vanilla to medium-stiff peaks. The cream should hold its shape firmly when the whisk is lifted — soft peaks will cause the filling to ooze and the roll to flatten.
19. Fold in the marshmallow fluff (or cooled melted marshmallows) in two additions, using gentle folding motions until just combined. Visible streaks of marshmallow through the cream are desirable — they create pockets of chewy sweetness that recall biting into a Fifteen.
20. Fold in the toasted desiccated coconut for texture and that essential Fifteen flavor note.

ASSEMBLE THE SWISS ROLL:
21. Gently unroll the cooled sponge. Do not worry about slight cracking — the filling will hide it.
22. Spread the cherry compote in a thin, even layer over the sponge, leaving a 2.5cm (1-inch) border along the far short edge to prevent filling from squeezing out when rolled.
23. Spread the marshmallow cream over the compote in an even layer, slightly thicker at the near edge and tapering toward the far edge. Use about three-quarters of the cream. Reserve the remainder for patching or garnishing.
24. Re-roll the sponge tightly from the short end, using the towel to help guide it and applying gentle, even pressure. Peel the towel away as you go. When complete, place seam-side down.
25. Wrap snugly in cling film, gently pressing the roll into a round shape. Twist the ends like a candy wrapper to maintain even pressure.
26. Refrigerate for at least 1 hour, or up to overnight. The chilling time allows the filling to set firmly, which helps the roll hold its round profile.

FINISHING:
27. Unwrap the Swiss roll and trim both ends at a slight angle with a sharp serrated knife for a clean presentation.
28. Transfer to a serving board or plate. Dust lightly with powdered sugar, scatter a few halved glacé cherries along the top, and finish with a light sprinkle of toasted coconut.
29. Slice with a sharp serrated knife, using a gentle sawing motion to preserve the spiral.