For the creamy blueberry jam, rinse the blueberries with cold water and carefully sort them.
Slit the vanilla pod lengthwise and scrape out the pulp. Place in a saucepan with the blueberries, preserving sugar and citric acid and bring to a boil. Bring to a bubbling boil for 4 minutes. Remove the pot from the heat and puree the mixture with a blender. Stir the mascarpone and cream into the blueberry mixture. Let it boil again for 3 minutes. Now make the jelly test. Drop some of the jam onto a cold plate. If it sets, the jam is ready. If not, let the mixture boil a little longer.
Immediately pour the blueberry jam into prepared twist-off jars. Drizzle a little alcohol over the top. Place on a tea towel with the lid down and let cool.