Gently punch down dough and divide in half. Roll into 2 12x18 inch rectangles on a lightly floured work surface. Spread maple-butter mixture evenly over both rectangles. Sprinkle each with half the brown sugar and walnuts. Roll tightly into logs, starting at the long edge, and pinch seams together. Cut each log into 6 3-inch pieces for a total of 12 buns. Place in muffin tins cut side up, cover and allow to rise for 30 minutes. Heat oven to 325°F. Bake until golden brown, 28 to 30 minutes.