1) Preheat the oven to 190C/Gas 5.
2) Begin by soaking the sultanas. Pour hot water over the sultanas and add the rum. Cover with cling film and set aside while you prepare the rest of the dish - let rest for at least 45 minutes
3) Split the pears down the middle, retaining the stem and skin. Using a melon ball scoop, remove the cores. Add the brown sugar and butter to a large nonstick skillet over medium-high heat until just melted. Add the lemon juice and pears, cut side down, and baste with the melted butter and sugar. Pop into the oven for 15 to 17 minutes until the pears are tender. When done, remove them from the oven and baste once more.
4) Whisk the mascarpone cream gently to loosen it up. Strain the raisins and gently fold into the cream.
Serve the pears on a plate, topped with a scoop of mascarpone cream and drizzled with the pear pan juices. Top with the crumbled amaretto biscuits.