Combine liver, Madeira, herbs and garlic in a bowl, refrigerate for 2 hours to marinate. Drain livers from marinade, set aside. Transfer marinade to a small saucepan, bring to the simmer over medium-high heat, stir occasionally until reduced to 1 tbsp (1-2 minutes).

Melt butter in a frying pan over low heat, add livers, turn occasionally until cooked medium-rare and pink inside but not coloured (10-12 minutes). Remove with slotted spoon, transfer to food processor. Strain half the butter through a sieve, set aside (discard remainder).

Add reduced marinade to livers (remove bay leaf). Squeeze excess water from gelatine, add to food processor, process until very smooth. Add reserved butter, process to combine, season to taste with sea salt, white pepper and nutmeg. Spoon into a 900ml-capacity shallow tray lined with plastic wrap, smooth top, refrigerate until firm (1-2 hours).

For cassis jelly, warm cassis in a small saucepan over low heat. Squeeze excess water from gelatine, add to cassis, remove from heat, stir to dissolve, cool slightly. Pour over pâté to form a thin layer, refrigerate until set (3-4 hours).

For brioche croûtons, preheat oven to 160C. Cut 5cm-diameter rounds from each brioche slice, place on a baking tray, bake until golden (5-6 minutes), cool.

Remove pâté from tray, cut rounds with a warmed 5cm-diameter cutter, place on brioche, garnish with baby parsley and serve.