Preheat the oven to 350°F. Line a 9 by 13 inch baking pan with parchment paper, leaving a little extra paper over the sides to make the bars easier to lift out later.

Beat the softened butter and granulated sugar together until smooth and creamy. Mix in the vanilla.

Add the flour and gently work it into the butter mixture with a wooden spoon or spatula until a soft dough forms. Press the dough evenly into the bottom of the prepared pan.

Bake for 12 to 15 minutes, until the surface looks set and the edges are just beginning to turn lightly golden. There is no need to prick the shortbread with a fork; any slight puffing will be covered with the mincemeat. Once baked, remove the pan from the oven and place it on a towel or cooling rack.

Add the mincemeat in small dollops all over the warm shortbread base. Once all the mincemeat has been added, gently spread it into an even layer with a spatula or the back of a spoon.

Whisk the flour and brown sugar together until well combined, breaking up any brown sugar lumps as you go. Add the softened butter and work it into the flour mixture with clean hands until the streusel is crumbly. Stir in the sliced almonds.

Crumble the almond streusel evenly over the mincemeat layer. Return the pan to the 350°F oven and bake for 25 to 30 minutes, until the almond streusel is lightly golden and the mincemeat is bubbling a little around the edges.

Remove from the oven and place the pan on a towel or cooling rack.

Serve warm as a dessert with a spoonful of whipped cream and a light dusting of icing sugar.

For smaller Christmas squares, let the bars cool completely. Use the parchment paper to lift them from the pan and place them on a cutting board. Dust with icing sugar, then cut into approximately 2 inch squares.