Blackberry, White Chocolate, Lemon and Elderflower Torte

THE SAVOY SPONGE

STEP 1: PREPARE THE TIN
Preheat the oven to 200°C (180°C fan / 400°F). Base-line a 20 cm loose-bottomed round tin with parchment and grease it. Sprinkle a little caster sugar (/interesting-ingredients/caster-sugar)around the sides and tap out the excess, giving the fatless sponge something to climb.

STEP 2: WHISK THE YOLKS
Whisk the egg yolks with the caster sugar until smooth, greatly increased in volume and very pale. This aeration, not the baking powder, carries the rise, so take it almost white.

STEP 3: ADD FLOUR AND FLAVOUR
Sift in the potato flour a little at a time, whisking after each addition, then beat in the lemon zest and lemon extract. The batter will seize and stiffen sharply as the potato flour goes in; this is expected.

STEP 4: FOLD AND BAKE
Whisk the egg whites to stiff peaks in a clean bowl. Slacken the batter with a spoonful of the whites, then fold in the rest gently with a metal spoon until just combined. Fold in the baking powder last. Pour into the tin and bake for about 40 minutes, until risen and set; do not open the door early. Cool in the tin until firm, then turn out and cool completely before cutting. The sponge should stand about 6 cm deep.

THE BLACKBERRY CURD

STEP 5: COOK THE BERRIES
Reserve 19–21 of the best blackberries for decoration. Put the rest in a pan with the water and the orange juice and zest, bring to the boil, then simmer for about 5 minutes until mushy. Press thoroughly through a sieve back into the pan.

STEP 6: THICKEN THE CURD
Over medium heat, stir in the caster sugar and butter until dissolved. Blend the cornflour with 2–3 tbsp cold water to a paste and whisk it in, stirring constantly until thick and bubbling, at least 3 minutes. Off the heat, stir in the black raspberry liqueur. Cover the surface with cling film and chill until firm.

THE ELDERFLOWER SYRUP

STEP 7: MAKE THE SOAK
Warm the caster sugar and water gently until dissolved, then bring to the boil until very slightly thickened. Cool, then stir in the elderflower liqueur. This soak keeps the naturally dry Savoy sponge moist and carries the elderflower note through every layer.

THE SWISS MERINGUE BUTTERCREAM

STEP 8: MAKE THE MERINGUE
Combine the egg whites and caster sugar in a heatproof bowl set over simmering water. Whisk by hand until the sugar has fully dissolved and the mixture reaches 60°C. Transfer to a mixer and whisk on high for 3–4 minutes until brilliant white, stiff, and the bowl feels cool.

STEP 9: ADD BUTTER, CHOCOLATE AND CURD
Switch to the paddle on medium speed. Add the soft butter a teaspoon at a time, letting each addition disappear before the next. When all the butter is in, trickle in the melted white chocolate, then the vanilla extract,(/interesting-ingredients/vanilla-extract) then blackberry curd to taste and colour. Keep the buttercream cool in the fridge until needed.

ASSEMBLY

STEP 10: LAYER
Cut the cold sponge horizontally into three even layers (about 2 cm each). Set the first, browned side down, on the serving plate, protecting the edges with strips of parchment. Brush generously with elderflower syrup, spread with blackberry curd, then a layer of buttercream. Repeat for the second and third layers, brushing each with syrup.

STEP 11: COAT AND DECORATE
Chill briefly to firm, then apply a thin crumb coat over the top and sides. Chill again, then finish with a smooth final coat. Arrange the reserved, well-dried blackberries around the top, adding the mint leaves pointing outward just before serving so the crown looks fresh.