In a large skillet over medium heat, cook the diced bacon until crispy. Add the cipollini onions and cook until they become translucent. Stir in the oyster mushrooms and cook for another 5 minutes.

Add Rabbit and Seasoning

Add the diced rabbit meat to the skillet, cooking until browned. Stir in the grain mustard, white wine, chicken stock, thyme, salt, and pepper. Simmer for 10 minutes until the rabbit is cooked through and the mixture has thickened. Remove from heat and let cool.

Assemble the Pie

Preheat the oven to 200°C (400°F). Roll out one puff pastry sheet and place it in a pie dish. Fill with the cooled rabbit mixture. Roll out the second puff pastry sheet and cover the filling, sealing the edges by crimping with a fork. Cut a few slits in the top to allow steam to escape.

Bake the Pie

Brush the top of the pastry with beaten egg for a golden finish. Bake in the preheated oven for 25-30 minutes or until the pastry is golden and flaky.

Serve

Let the pie cool for a few minutes before slicing. Serve warm.