Place mustard into a small mixing bowl. Add Blueberry balsamic and whisk together. Slowly drizzle the olive oil into the balsamic mixture, whisking constantly until olive oil and balsamic are completely mixed and dressing begins to thicken. IF you used the Lemon olive oil you may not need the lemon zest. If you used a single varietal olive oil, add the lemon zest and whisk to incorporate.