Preheat the oven to 180°C/160° fan/350°F/gas 4. Grease and base line an 8 inch/20cm or 9 inch/23cm flan tin with removable base.
Roll out the puff pastry on a lightly floured surface then press into the tin and up the sides, trimming the edges. Arrange the pear slices over the pastry, pressing them firmly into the base.
Beat the Activia pear yogurt together with the eggs and vanilla extract. Pour the egg mixture over the pears and bake for 35-40 minutes or until the top is firm to the touch and beginning to brown. Cool in the tin, then remove and dust with icing sugar to serve.