In a large bowl, combine the flour, sugar, baking powder and salt. Add the butter and rub between your fingertips, incorporating the mixture as you work, until the butter forms pea-sized pieces.
In another bowl, combine the mashed bananas, milk and vanilla. Add to the dry ingredients and mix until just moistened. Shape the dough into a square.
Filling
In a bowl, combine the brown sugar and cinnamon.
On a lightly floured surface, roll out the dough into a 12-inch (30 cm) square. Sprinkle the brown sugar mixture over the entire surface of the dough.
Tightly roll the dough into a log. Flatten the log until it is 1 inch (2.5 cm) thick and 16 inches (45 cm) long. Cut into 6 rectangles, then halve each rectangle into 2 triangles. Place on the baking sheet, spacing them evenly.
Brush the scones with milk. Bake for 18 minutes or until golden brown. Let cool for 10 minutes before glazing.
Stir the maple butter with a spoon, then drizzle over the scones. Serve warm or cooled.
