Heat a pan over medium heat. Add in the butter and brown sugar. Allow the butter and brown sugar to melt together into a bubbly liquid. Then add in the banana slices in a single layer. Cook for 1 minute on each side until golden brown and caramelized. Remove the banana slices from the pan, leaving any excess sugar syrup in the pan.
In a bowl, whisk together the buttermilk, egg, and vanilla extract. In a separate large bowl, add in the flour, sugar, baking powder, and salt. Whisk the ingredients together until combined. Add in the cold diced butter and use a pastry cutter or fork to cut the butter into the dough until you get a mixture of butter pieces varying from pea sized to nickel sized.
Pour in the buttermilk mixture, caramelized bananas, and heath toffee pieces. Mix everything together with a fork until you get a scraggly clump of dough. Turn it onto a floured work surface and gently press the dough together into one mass. Be sure to not overwork the dough. Pat it into a 7 inch diameter circle. Wrap it in plastic wrap and freeze for 1 hour.
Preheat the oven 425℉. Line a baking sheet with parchment paper. Cut the dough in half. Then cut each half in half so you have quarters. Cut each quarter in half so you have 8 triangles. Place them onto the baking sheet spacing them 2 inches apart. Brush the tops with heavy cream or egg wash and sprinkle raw sugar on top. Bake them in the oven for 22-25 minutes until golden brown on the outside. Transfer the scones to a wire rack to cool.
In the meantime, whisk together the powdered sugar and coffee until you have a smooth glaze. When the scones have cooled, drizzle the glaze black and forth over each scone. Finish with a sprinkle of flaky salt and enjoy!