Peel the pears, cut into quarters and remove cores, then dice and toss with the vanilla sugar, brown sugar, lemon juice and chopped almonds.
Preheat the oven to 200°C (approximately 400°F).
Cut the pastry into squares about 20 x 20 cm (approximately 8 x 8 inches). Brush the squares with butter and arrange the pears over the lower third of each, dividing evenly. Turn the edges up and form into logs, then place with the seam down on a baking sheet lined with parchment paper. Brush with the remaining butter, sprinkle with almonds slivers and bake in the oven for 15 minutes until golden brown.
Remove from oven and serve dusted with powdered sugar.