Preheat the oven to 180°C.
Fry onions, celery, and carrot in oil for 10 minutes until softened.
Stir in flour and mustard, then gradually add ale and 250ml of water.
Add venison, jelly, herbs, and seasoning, then bring to a simmer.
Cover and bake in the oven for 1.75 to 2 hours until tender.
Adjust seasoning with salt, pepper, and lemon juice, then transfer to a pie dish.
Increase oven temperature to 200°C for the topping.
Rub butter into flour and salt until mixture looks like breadcrumbs.
Mix in milk to form a soft dough, then roll out to 2cm thickness.
Cut into 6cm rounds and arrange over the venison filling.
Brush with milk or egg and bake for 30 minutes until golden.