Preheat the grill to a medium heat.
For the cranachan, place the oatmeal onto a baking tray and place under the grill to lightly toast. Take care not to burn it. Remove from the heat and set aside to cool.
Meanwhile, place the cream into a bowl, add the whisky and icing sugar and whisk until it forms soft peaks when the whisk is removed.
Place four 6cm/3½in deep chefs' rings onto four plates. Spoon a little of the cream mixture into each ring to about 1cm/½in depth. Smooth down the top of the cream in the ring with a spoon to ensure a clean edge.
Layer some raspberries over each layer of cream, then repeat a layer of cream.
Repeat with a layer of raspberries followed by a layer of cream, until the ring is full. Be sure to finish with a layer of cream, smoothing the top over with a palette knife.
Dust the top and bottom of the filled rings with the toasted oatmeal, then place each ring into the centre of a serving plate. Carefully remove the chefs' ring from each cranachan, using a mini-blowtorch to heat and loosen the rings first if necessary.
For the raspberry sauce, place the raspberries, lemon juice and icing sugar into a food processor and blend until smooth. Pass the sauce through a sieve into a bowl.
To serve, top each cranachan with a couple of raspberries and a sprig of mint and spoon the raspberry sauce around the edge.
