Place the vinegar, sugar, onion, mustard seeds, ginger, bay leaf, thyme, and salt in a saucepan. Bring to a simmer over medium heat and simmer until reduced by half.

Add half of the blueberries and continue simmering until thickened, and the blueberries have burst.

Remove from heat and stir in remaining blueberries.

Pack in a clean container and refrigerate.