Firstly, do the prep work. Slice the leeks, peel and finely chop the onion and garlic. On a separate board, then dice the chicken.
Place a Dutch oven over medium heat and add enough olive oil to cover the bottom of the pan. Once hot, add the leeks and onion along with a pinch of salt. Cook, stirring regularly, until softened, around 10 minutes.
Then, add the chicken and bacon. Cook for around six minutes until coloured and mostly cooked, then add the garlic. Stir together, and cook for another two minutes. If the pan becomes dry, add more oil.
Next, add a teaspoonful of fennel seeds, and two tablespoonfuls of wholegrain mustard. Mix together well. Preheat the oven at this point to 180C/250F.
Add chicken stock and allow this to gently simmer, stirring occasionally, until the liquid has mostly evaporated and what’s left is quite thick, like the consistency of custard.
Next, add heavy cream and mix together. Let this gently simmer too until it thickens the mixture to the same consistency as before. Taste, and adjust seasonings if necessary, then remove from the heat.
Add the mixture to an oven dish, ideally one where it comes right to the top. Cover with a layer of puff pastry, ensuring that it is stretched out to hang over the edges of the oven dish. Make some heat vents in the top. Brush with egg yolk.
Place in oven and bake 20min.
