Preheat oven to 180°C/160°C fan forced. Grease a 20cm (base measurement), 4cm-deep square ovenproof dish. Cut croissants horizontally in half. Spread bases with butter; top with 16 pieces of the chocolate (4 pieces each). Replace croissant tops; cut each croissant sandwich in half crosswise. Transfer to prepared dish in a single layer.
2
Lightly whisk eggs in a jug. Add essence, caster sugar, cream and milk; whisk until combined. Pour mixture over croissants. Stand for 10 minutes, turning and pressing to submerge croissants in egg mixture.
3
Sprinkle top with frozen raspberries. Break remaining chocolate pieces in half; sprinkle on top. Bake for 35 minutes; cover with foil. Bake for 10 minutes more or until set at centre. Stand in dish for 5 minutes. Dust with icing sugar.