Preheat the oven to 180 C / Gas 4. Grease a 12 hole muffin tin.
To prepare the pastry, place the flour into a bowl then cut in the cold butter and rub between your fingers until the mixture resembles breadcrumbs. Add the sugar and mix well. Add the egg yolk to the mixture and stir, bringing the mixture together into a ball with a consistency that can be rolled. If needed, add a few drops of cold water.
On a floured work surface roll out the pastry and use a cutter to cut out circles of pastry to fit a 12 hole tart tin.
Blind bake the pastry for 10 to 15 minutes until golden brown. Remove the pastry from the oven and fill each will a tablespoon full of jam. Allow to cool then decorate the top with the fruit.