For the berry jam, mix the berries with lemon juice, vanilla sugar and preserving sugar. Puree with a hand blender. Bring to a boil in a large saucepan, stirring, and boil until bubbly, about 6-8 minutes.
Make a jelly test. Pour jam into prepared hot jars. Using an eyedropper, drizzle a few drops of alcohol over the top, light and seal immediately.