Chocolate yule log

Buttercream: whip powdered sugar, butter, a touch of unsweetened cocoa, a pinch of salt and a splash of coffee liqueur or extract on high until very light and fluffy; work cold butter with a spatula as needed.

Transfer to a bowl and stir in a big spoon of mascarpone for tang and lightness; set aside.

Line a baking sheet with parchment, a little butter under the paper to hold it, and brush it generously with melted butter.

Whisk the cocoa powder, salt and a little all-purpose flour together (sifting does a better job of breaking up cocoa lumps).

Whip five room-temperature large eggs with a little sugar on high for a few minutes until very pale, thick and fluffy.

Add the dry ingredients in two additions, a few seconds each on low, then finish by hand so the foam is not knocked out.

Spread the batter on the sheet, leaving a little space at the ends, and bang the pan on the table to knock out big bubbles.

Bake in the centre of a 400 degree oven eight to 10 minutes.

Dust a clean kitchen towel with powdered sugar over an area slightly bigger than the sheet pan.

Cool the cake a couple of minutes, loosen the edges with a knife, dust the top with powdered sugar, flop it onto the towel and peel off the parchment.

Dust again with powdered sugar and roll up gently in the towel without pressing; cool rolled 15 minutes so the sponge keeps the memory of the roll.

Unroll, dollop the filling about and spread it evenly, then roll back up with a light touch, using the towel to start.

Dust with a little more sugar, wrap in two layers of plastic and chill in the fridge a few hours until completely cold.

Ganache: pour hot boiling cream over dark chocolate chips, leave about a minute, then stir until smooth; it thickens as it cools.

Trim the end, then make an angled cut about three inches from one end; set the log on a parchment-lined sheet pan and stick the cut piece to the side with buttercream as a branch.

Cover the log with ganache, leaving the ends showing the swirl; chill 15 or 20 minutes until firm, then drag a knife tip through for bark texture.

Chill thoroughly; serve on a platter dusted with cocoa and powdered sugar, optionally with gingerbread dirt, meringue mushrooms and rosemary sprigs.

Optional: brush or drizzle Kahlua on the sponge before rolling.