In a small saucepan over medium heat, combine blueberries, balsamic vinegar, Dijon mustard, olive oil, thyme, lemon zest, and salt. Let it simmer for 6–8 minutes, stirring and gently smashing some of the blueberries with the back of a spoon until the mixture thickens into a syrupy glaze. Taste and adjust with a touch of maple syrup if more sweetness is needed. Remove from heat and set aside.
½ cup blueberries, 1½ tbsp balsamic vinegar, 1 tsp Dijon mustard, 1 tsp olive oil, ½ tsp thyme, ½ tsp lemon zest, 1 pinch salt