Heat some olive oil in a pan on high heat, then add the prosciutto and cook for 2 minutes on each side or until crisp. Set aside to cool, then tear into smaller pieces.
Roughly chop walnuts.
Quarter avocados and place in a bowl. Add lime juice, olive oil and 2 teaspoons of spice, then toss lightly to coat.
Arrange avocados in a serving dish and sprinkle with walnuts, coriander, prosciutto and remaining spice.