Preheat the oven to 347° F. In a bowl, sift the flour with the baking powder.
Add the sugar, a pinch of salt and the jam. In another bowl blend together the mix, the oil and the egg, then add these to the dry ingredients and mix everything with an electric beater.
Spoon the mix into cupcake molds and add a blueberry to the center of each. Put in the oven for 20-25 minutes. Leave to cool before decorating. Meanwhile make the frosting. Beat together the cream, mascarpone cheese and the confectioner’s sugar using a whisk until they are a dense cream.
Transfer the mix to a pastry bag fitted with a star-shaped tip.
Coat each muffin with a light layer of Rigoni di Asiago blueberry jam before decorating with the frosting. Finish each cup cake with a fresh blueberry. Keep in the fridge until ready to serve.