Heat oven to 375 degrees. Place a Silpat (French nonstick baking mat) or parchment paper on a baking sheet; place six 2 3/4-by-2-inch pastry rings on it. Cut parchment paper into six 10-by-3-inch strips; use them to line molds (paper will extend above rims).
Place softened butter, 3/4 cup sugar, and honey in bowl of an electric mixer fitted with the paddle attachment. Beat on medium speed until fluffy, about 1 minute. Add eggs; beat 1 minute more.
Whisk flour, cornmeal, and baking powder together in a medium bowl; add to butter mixture in mixer bowl. Beat until combined. Slowly pour in milk, beating on low, until just combined. Fold in blueberries. Divide dough among molds (do not pack too firmly; each will take about 1 cup). Brush tops with cold water; sprinkle 1 teaspoon sugar over each.
Bake until tops are browned, centers are set, and a cake tester inserted in center of muffin comes out clean, about 30 minutes. Let cool in pans 5 minutes. Tie kitchen twine around muffins to hold parchment. Serve at once.