Place half the raspberries in a bowl. Heat the vinegar until in a saucepan until it starts to bubble, then pour it over the raspberries and leave to steep for 50 minutes. Strain the raspberries, pressing the fruit gently to extract all the juices but not the pulp. Whisk the strained raspberry vinegar together with the oils and seasonings. Set aside.

Carefully halve each avocado and twist out the stone. Peel away the skin and slice the flesh straight into the dressing. Stir gently until the avocados are completely covered in the dressing. Cover tightly and chill in the fridge for about 2 hours. Meanwhile, separate the radicchio leaves, rinse and drain them, then dry them on kitchen paper. Store in the fridge in a polythene bag.

To serve, place a few radicchio leaves on individual plates. Spoon on the avocado mixture and garnish with the remaining raspberries.