Peel and thinly slice the shallots and garlic. Bring to a boil with the bay leaf, cloves, coriander, fennel, vinegar, salt, sugar, and 200 ml (approximately 7 ounces) of water. Boil for 2-3 minutes then pass through a fine strainer into a bowl. Mix in the mustard seeds and let soak, covered, for three days. Puree coarsely with an immersion blender, then transfer into jars. Seal tightly and let rest for 1 week.