1.

Cut the tuna steak into a 3cm square block, season and rub all over with olive oil

2.

Heat non-stick fry pan and sear tuna over high heat on each side until golden but still pink in the middle. Set aside

3.

Combine the mayonnaise, crème friache and cornichons in a bowl. Place 1 teaspoon of the mayo mixture into each tart case and place a piece of thinly sliced tuna on top. Garnish with a sprig of chervil and serve immediately