In a blender blend flour, salt, eggs, milk, and 4 tablespoons butter, scraping down sides, 30 seconds.
Brush eight 1-cup popover tins or 2/3-cup custard cups with some remaining fat and heat in middle of oven 5 minutes, or until hot. Fill tins or cups half full with batter and sprinkle top of each popover with about 1/2 teaspoon rosemary. Bake popovers 45 minutes, or until golden brown and crisp.
