Taste a blueberry. Is it sweet and flavorful? Tart? If it is very sweet I recommend starting with 1 Tbsp sweetener. Add more after the vinaigrette is blended, if needed.
Gently smash the garlic clove with your hand to loosen the skin. Remove it and discard.
Place all the ingredients in a bowl (for an immersion blender) or in the food processor or blender.
Run on high for 30 seconds - 1 minute. The mixture should be smooth and magenta pink.
Run the mixture through a fine mesh strainer to remove the blueberry skin.
Taste. Do you prefer it more sweet? Stir in 1-2 tsps of sweetener. Prefer it more sour? Add 2 tsps vinegar. Is it missing that indescribable something? Stir in 2 pinches salt. Is it too sour? Add another Tbsp of oil and a tsp of sweetener. Is it too bitter? Stir in a couple of pinches of salt.
Store this vinaigrette in the refrigerator. It will stay fresh for at least a week, If it thickens too much after refrigerating, heat it in the microwave for 10-15 seconds.