If the puff pastry isn't already rolled, roll out the pastry to about 5mm (1/4") thickness in either a rectangular or round shape. Place on a baking sheet covered with baking paper.
Prepare the almond paste: in a bowl, stir together the ground almonds, honey, 15g of the softened butter and Calvados (or Pommeau). Spread evenly over the pastry, leaving a small space (1cm) in from the edge.
Peel and core the Granny Smith apples and slice them as thinly as possible using a good, sharp knife. Quickly arrange them in rows on the pastry.
Melt the remaining butter, stir in the muscovado sugar and brush on top of the apples. Scatter with slivered almonds, if using and bake in the oven for about 20 minutes.
In a chilled bowl, whisk the whipping cream with the mascarpone and add the Calvados or Pommeau towards the end, just as the cream thickens.
* Pommeau is a lighter apple wine from Normandy made with 1/3 Calvados and 2/3 non-fermented apple juice. If you can find this easily, this is fabulous to replace Calvados.Serve with a dollop of the Calvados or Pommeau cream - or, if you prefer ice cream, replace the Drambuie to make this no-churn Calvados or Pommeau Ice Cream.