Cut speck into 1cm cubes, and place into a cold saucepan to render its fat. Cook on medium-high until golden-brown. Transfer to a bowl.

Cut chicken into cubes, coat with mustard, and sear it in the same saucepan. Transfer to bowl of speck.

Note: more cooking time on chicken occurs in the following steps, do not worry if it's not fully cooked in this step.

Sauté onion in the same saucepan until translucent. Add leeks, and cook until they relax and are fragrant, stirring occasionally. Add wine and stock, turn up the heat, and cook to reduce by half.

Return speck and chicken to saucepan, add garlic, cornflower, herbs, salt and pepper. Stir to combine and allow to cook for 5 minutes. Add peas, season to taste.

Remove from heat, and allow to cool. If you're time-poor, place the filling into a baking tray, and place in your freezer for a quick turn-around. Its best your filling is cooled, to ensure a perfectly crispy crust.

Once your filling is cooled, preheat your oven to 180°C, and place filling evenly into a baking dish. Top with sheets of puff pastry, and make a small slit in the centre to allow for air to escape while baking.

Brush pastry with whisked egg for a crisp, golden top, and finish it with a sprinkle of sesame seeds.

Bake for 30 minutes or until the pastry is golden-brown.

Serve with a fresh, leafy-green salad, and devour.