Clementine and Chestnut Torte

STEP 1: INFUSE THE MILK

Warm the milk to just below a simmer, then take it off the heat. Bruise the lemon verbena leaves between your fingers and drop them in. Cover and leave for 30 minutes, then strain, pressing the leaves to draw out every drop. Bring the infused milk back to room temperature before you use it. Verbena is volatile and fades with heat - a warm infusion, never a boil, is what keeps the perfume in the crumb.

STEP 2: MAKE THE CLEMENTINE CURD

Whisk the egg yolks, caster sugar and cornflour in a heatproof bowl until pale. Whisk in the clementine juice, lemon juice, clementine zest and salt. Set the bowl over barely simmering water and stir constantly, reaching into the corners, for 8-12 minutes, until the curd thickly coats the back of a spoon and holds a drawn line. Off the heat, beat in the cold butter a few cubes at a time. Sieve into a clean container, press cling film directly onto the surface and chill for at least 2 hours. It will set considerably as it cools.

STEP 3: BAKE THE CHESTNUT SPONGE

Heat the oven to 180C / 350F (fan 160C / 325F). Grease three 20 cm / 8 in sandwich tins and base-line them with parchment paper. Sift the chestnut flour, cornflour, baking powder and salt together twice - chestnut flour lumps and compacts and will not aerate on its own - then stir through the ground almonds. Cream the butter and caster sugar with an electric whisk until genuinely pale and light, a good 4-5 minutes. Beat in the eggs one at a time, then the clementine zest. Fold in the dry mixture in three additions, alternating with the infused milk and finishing with dry. Stop the moment it is homogeneous; chestnut flour toughens fast under a heavy hand. Divide by weight between the three tins - a torte lives or dies on even layers - and level the tops. Bake for 22-26 minutes, until a skewer comes out with a few moist crumbs and the edges are just shrinking from the tin. Cool for 10 minutes in the tins, then turn out onto a cooling rack.

STEP 4: MAKE THE LEMON VERBENA SYRUP

Dissolve the caster sugar in the water over a low heat and bring to a bare boil. Take it off the heat, add the bruised verbena leaves and steep for 20 minutes, then strain and cool. The second infusion earns its place - a single one does not survive the bake.

STEP 5: MAKE THE LEMON-OIL BUTTERCREAM

Whisk the egg whites and caster sugar in a scrupulously clean bowl set over simmering water, stirring, until the sugar has fully dissolved and the mixture reaches 71C / 160F. Whisk on high until the meringue is stiff, glossy and - critically - the bowl is cool to the touch. Rushing this is the single most common way this buttercream fails. Switch to the paddle and add the butter a few cubes at a time. It will curdle and look ruined; keep going and it will come back smooth. Beat in the lemon oil and salt last, on low.

STEP 6: ASSEMBLE THE TORTE

Level the sponges if they have domed, then brush each cut face generously with the verbena syrup. Pipe a thin band of buttercream around the rim of the first layer and spoon the chilled clementine curd inside the dam - the buttercream wall stops the curd escaping under the weight of the layer above. Repeat with the second layer, then set the third on top. Coat the outside in a thin crumb layer of buttercream, chill for 20 minutes, then apply the final coat and smooth it with an offset spatula.

STEP 7: FINISH THE TOP

Segment the clementines fully, removing every trace of membrane, and drain them well on kitchen paper - wet segments will bleed into the buttercream. Arrange the segments radially, setting them so that the gaps between them, not the segments themselves, fall on the cutting lines: twelve gaps for twelve slices, so the knife passes between the fruit and every portion comes away intact. Brush the segments with warmed apricot glaze for shine and to seal them against drying, then finish with a few small verbena leaves. Chill for 30 minutes to set, then bring back to cool room temperature before serving - buttercream served fridge-cold tastes of nothing.