Line a baking tray with cling film.
Mix 110g butter with wild garlic, roll into a cylinder in greaseproof paper, and chill until set.
Melt 65g butter with 110ml water in a pan, then stir in flour until the mixture leaves the pan sides.
Beat in eggs one at a time, followed by mashed potato and salt.
Spoon the potato mixture onto the tray and chill.
Heat a deep-fat fryer to 170°C.
Slice the chilled garlic butter into rounds.
Shape potato mixture around butter slices to form balls and fry for 3 minutes until golden.
Preheat the oven to 200°C.
In a hot pan, seal lamb with oil, rosemary sprig, and garlic, then add carrots to coat.
Roast lamb and carrots in the oven for 8 minutes, turning halfway through.
Remove lamb from the pan and let it rest.
Deglaze pan with vinegar, add stock, simmer for 5 minutes, then whisk in 25g butter.
Preheat the grill to high.
Process brioche, chopped rosemary, and parsley in a food processor into crumbs.
Brush lamb with maple syrup and mustard mixture, press on crumbs, and grill for 3 minutes.
Slice lamb and serve over carrots and sauce with choux potatoes.