Two puddings in one! The gooey meringue hides a syrupy, crumbly filling that is offset by the sharpness of the pears.
Preheat the oven to 200°C/180°C fan/400°F/Gas 6.
Make the meringue. Put the egg whites in the bowl of a stand mixer fitted with the whisk attachment and whisk on medium speed until they form stiff peaks. Increase the speed to medium–high, add the sugar 1 teaspoon at a time, whisking continuously. Continue to whisk for about 4–5 minutes, until the meringue is thick and glossy. Using a metal spoon, fold in the lemon zest.
Spread the meringue into the prepared Swiss roll tin and smooth out with a spatula. Sprinkle the crushed pecans evenly over the meringue and then bake for 10 minutes, until browned. Reduce the heat to 180°C/160°C fan/350°F/Gas 4 and bake for a further 8–10 minutes, until the meringue is firm to the touch.
Meanwhile, make the treacle tart filling. Place the bread in a food processor and pulse for a few seconds to form breadcrumbs. Place the golden syrup in a medium pan with the lemon juice over a medium heat. Warm through for 1 minute to loosen the syrup and incorporate the lemon juice. Remove from the heat and stir in the breadcrumbs. Transfer to a bowl and allow to cool.
Remove the meringue from the oven and invert it onto the wire rack lined with baking paper. Carefully, peel off the uppermost sheet of baking paper and leave the meringue to cool.
Meanwhile, make the cream filling. Use an electric hand whisk to whisk together the cream and mascarpone until the mixture just holds its shape. Place 3 tablespoons into a piping bag fitted with a large round nozzle.
Keeping the meringue on the sheet of baking paper, transfer it to the worktop. Use a palette knife to spread the remaining cream filling over the meringue in a thick layer. Spread the treacle tart filling evenly over the top, then finally sprinkle over the chopped fresh and dried pears.
With the short end of the roulade closest to your body, use a knife to score the meringue 2.5cm in from the short edge. Fold over the scored edge and, using the baking paper to help you, tightly roll up the roulade. Place the roulade, seam-side down, on a serving plate.
Pipe rosettes of cream all along the top of the roulade. Place a whole pecan in each of the 6 rosettes.