Put the syrup, blueberries, and thyme springs, if using, into a small saucepan and bring to a boil. Reduce heat and simmer while you make the pancakes.
Remove the thyme sprigs just before serving.In a medium saucepan, combine the cornmeal and cold water. Bring to a boil, whisking constantly. Simmer over medium heat until thickened, about 4 to 5 minutes.In a small bowl, beat together milk, egg, honey, and vanilla.
Add to the polenta (boiled cornmeal).In a large bowl, whisk together flour, baking powder, salt, and lemon zest. Make a well in the center and stir in the polenta custard.
Heat a large griddle and brush it with butter.Ladle enough batter onto the griddle for 4-inch cakes. If the batter is too thick to spread on its own, add a bit more milk. Cook the pancakes over moderate heat until bubbles appear on the surface and the top of the pancake looks dry. Flip the pancakes and cook until puffy and browned on the bottom, about 2 minutes.
Transfer to warm plates and repeat with remaining batter.
