Method

• 1.
  Preheat oven to 180°C/160°C fan-forced.
• 2.
  To cook the chicken, place stock in a saucepan and bring to the boil over high heat. Add chicken and return to the boil. Remove from heat, cover and stand for 20 minutes, or until chicken is cooked through. Drain and set aside to cool. Finely chop chicken and toss through a pinch of salt flakes. Set aside.
• 3.
  Meanwhile, place oil and prosciutto in a frypan over medium-high heat. When hot, cook prosciutto for 1-2 minutes each side, until crisp. Remove and drain on paper towel. Set aside for 5 minutes to cool slightly, then finely chop 4 slices and place in a bowl. Break remaining 1 slice prosciutto into small pieces and set aside.
• 4.
  To make the bechamel, melt butter in a saucepan over high heat. Add flour and cook, whisking, for 2 minutes, or until thickened. Gradually add milk, whisking well after each addition. Bring to the boil, then reduce to a simmer and cook, whisking, for 3 minutes, or until thickened. Remove from heat and stir through tarragon, Gruyere, paprika, chopped chicken and chopped prosciutto.

• 5.
  When ready to serve, arrange pastry cases on a baking tray, brush with egg and bake for 6-8 minutes, until golden.
• 6.
  Fill warm pastry cases with warm or cooled chicken mixture. Sprinkle with broken prosciutto pieces, extra Gruyere and paprika, and chervil, if using, to serve.