For the filling, heat the sugar, cinnamon stick, blueberries and butter in a pan, stirring continuously, until the mixture is simmering. Continue to simmer for 3-4 minutes, or until the sugar has melted and has turned golden-brown in places and the blueberries have broken down.
Add the peach liqueur and bring to the boil for one minute, stirring well. Remove the pan from the heat and set aside.
For the crumble topping, place the muesli, flour, brown sugar and butter into a large mixing bowl. Rub together using your fingertips until the mixture resembles breadcrumbs.
Transfer the crumble mixture to a dry frying pan and toast over a medium heat until golden-brown.
For the honeyed mascarpone, mix together the honey and mascarpone until smooth and well combined.
To serve, divide the filling mixture equally among two ramekins. Sprinkle over the crumble topping. Place the ramekins onto serving plates and spoon the honeyed mascarpone alongside.