Start my making the berry compote. Put all the berries into a large pan on a medium high heat and add the sugar and a little water, all if needed. Let the berries cook down, stirring to make sure it isn't sticking. When the liquid has thickened and evaporated slightly, take off the heat and allow to chill completely until thick and sticky.
Meanwhile make the chocolate sauce, melt the butter in a small pan with the sugar. Once the sugar has dissolved add the cream, vanilla and stir through the melted chocolate. Once all well combined take off the heat and allow to cool.
Start layering up the sundae however you like, finish with a glacier cherry and grating over the chocolate. Save any chocolate sauce and compote in the fridge for another day.