Heat a tablespoon of olive oil in a large pan, dice the onion and gently cook it in a pan over low heat for 5-7 minutes without colouring it.
Dice your rabbit, pheasant and chicken into 1'' dice and add to the pan, brown the meat over medium heat, add rosemary and cook for 2 more minutes, then pour in the wine, let the alcohol burn off and then add your stock, bring to a boil and turn the heat down. Gently simmer the mixture for 1.5 hours, stirring occasionally and adding more stock if a bit dry. At the end of the cooking time your meat should be very soft and the whole filling look like it's swimming in gravy but not too soupy.
Adding vegetables is optional. Slice the carrot and potato and add to the mixture, cook for 5-7 minutes, then add frozen peas.
Stir in your creme fraiche for the creamy consistency and cool your mixture so it doesn't melt the pie crust when you pour it in.
Preheat your oven to 200C/400F.
Roll out your pie crust to fit your pie plate making sure the bottom crust goes up the sides and hangs over the edges. Fill your pie with the meat mixture and cover it with the top crust. If you feel especially creative you can cut out rounds with a pastry/cookie cutter and assemble a pie topper out of them, overlapping them slightly and brushing each circle with an eggwash to make individual circles stick to each other and to give your pie an attractive shiny and golden finish.
If you opt out for the traditional top crust don't forget to make slits so the steam can escape. Bake at 200C/400F for 30 minutes until the pie is golden and the filling is bubbling.