1 Rinse the blueberries and drain well; thaw frozen berries. Rinse lemon under hot water, wipe dry and finely grate the zest. Squeeze the lemon. Bring 2 tablespoons lemon juice, two-thirds of the blueberries, the sugar and cassis or syrup to a boil in a pot. Cook over medium heat for 5 minutes, stirring.
2 Pass mixture through a fine sieve into a bowl, pressing with a ladle to extract as much juice as possible.
3 Add the remaining blueberries to the strained liquid and let cool completely.
4 Stir together the buttermilk, honey, soy creamer and lemon zest until smooth. Chill at least 1 hour. To serve, divide the cold soup among soup plates and spoon the blueberry compote in the middle of each. Crumble Amarettini over the top.