Place blueberries, water, and sugar in saucepan. Bring to boil. Lower heat to simmer and cook until berries soften, give up some juice, but keep their shape. While berries cook, dissolve cornstarch in water. Add to softened berries and continue to cook, stirring, until mixture thickens (if you like a thicker “preserve,” add additional cornstarch-water mixture). Remove from heat and taste for sweetness; stir additional sugar into mixture, if preferred, and stir until dissolved. Add lime juice, zest, and 1 teaspoon thyme, if using. Cool and refrigerate, bringing to room temperature at serving time. Heat oven or toaster oven to 350 degrees. Split biscuits in half. Top each half with cheese curds. Bake 5 minutes to toast biscuits and warm curds. Remove from oven. Top with blueberry preserves and thyme. Serve with blueberry jam.