Preparation

1. Wash the sweet potatoes and cut into long strips about 1 cm thick. Peel and thinly slice the red onion. Leave the sweet potatoes to stand in ice-cold water for 15 min. Heat the oil in the deep fryer.

2. Drain the sweet potato strips and pat dry with paper towels. Cook for 5 min in the deep fryer until golden brown. Remove from oil and drain on newspaper covered with kitchen roll. Repeat with the red onion rings.

3. Preheat oven to 230°C (gas mark 8). Mix the sage, nutmeg, mustard, coriander and a turn of the pepper mill in a bowl. Brush the roast with this mixture and roll it in the slices of Parma ham.

4. Line a casserole dish with a 2 cm thick layer of coarse salt. Place the roast on top. Cover with the remaining salt (2 cm thick).

5. Bake for 1 h 15. Leave to rest for 15 min before breaking the crust. Break it open and remove the salt. Cut the roast into thin slices. Divide between the rolls, cut in half, and add the mustard and red onion rings.

6. Serve with sweet potato fries sprinkled with Espelette pepper and fleur de sel.