The Blackberry Spritz, from the James Beard Foundation, is a great example of how jams and fruit preserves can add wonderful flavor and velvety body to a cocktail.
The original recipe calls for Campari, a bitter citrus apéritif. If you have a sweeter tooth, you can use a sweet orange apéritif like Aperol instead. Your jam or preserves can have seeds in it or not – if it does, be sure to strain the drink through a fine wire mesh strainer before you serve it.
Blackberry jam is specified, of course, but it’s quite lovely with other berry jams as well.