Melt 40g of the butter in a large frying pan over medium heat.
Add the nuts and fry for 2-3 minutes, shaking the pan regularly and being careful not to burn the butter. Using a slotted spoon, remove nuts from the pan and set aside.
Add the remaining butter and the brown sugar to the pan and cook over low to medium heat until the sugar caramelises. Add the prickly pears and cook until slightly softened, about 4 minutes.
Serve the prickly pear halves drizzled with the pan juices, topped with the nuts and accompanied by a scoop of vanilla ice cream.