Chateaubriand Bombe (Bombe à la Chateaubriand)

Ingredients

• 2 pints milk (Whole milk is best; this forms the base of the custard)
• 4.5 ounces castor sugar (For the custard base; caster sugar is the modern equivalent of castor sugar)
• 1 pod vanilla pod (Split lengthways into thin shreds to release maximum flavour)
• 4 sheets gelatine sheets (Use standard leaf gelatine; soak in cold water before adding to hot milk)
• 12 yolks raw egg yolks (Use fresh, large eggs; yolks only, no whites needed)
• 0 a few drops essence of vanilla (Add to the green custard portion only; use pure vanilla extract)
• 0.25 pint orange-flower water (For the green custard portion; available from Middle Eastern grocery shops or online)
• 0 a small amount apple green food colouring (Tint the green custard portion to the colour of pistachio; use a natural green food colouring if preferred)
• 0.5 pint whipped cream (Whip to soft peaks before folding into the partly frozen green custard)
• 0.5 teaspoon castor sugar (To sweeten the whipped cream)
• 3 ounces blanched sweet almonds (Pre-blanched almonds with skins removed; available ready-blanched in most supermarkets)
• 0.5 ounce fresh butter (Unsalted butter; used to toast the almonds)
• 1 ounce castor sugar (To caramelise and coat the almonds during toasting)

Instructions

1. 1Pour 2 pints of milk into a medium saucepan. Add 4½ ounces of castor sugar and 1 vanilla pod split lengthways into thin shreds. Place over a medium heat and bring just to the boil, stirring gently to dissolve the sugar. As soon as you see it begin to bubble, reduce to the lowest heat possible or move the pan to the side of the hob. Cover with a lid and leave for about 15 minutes — the milk must stay hot but must not boil. This gentle infusion draws the full flavour out of the vanilla.
2. 2Soak the 4 gelatine sheets in a bowl of cold water for about 5 minutes until soft and floppy. Squeeze out the excess water with your hands, then add the softened gelatine sheets to the hot vanilla milk. Stir well until fully dissolved — the milk must still be hot enough to melt the gelatine. If needed, warm it gently over a low heat for a moment, but do not let it boil.
3. 3Place the 12 egg yolks in a large heatproof bowl and whisk them together until smooth and slightly pale. Now you need to temper the eggs so they do not scramble: slowly pour the hot gelatine-infused milk into the egg yolks in a thin, steady stream, whisking constantly as you pour. This gradually raises the temperature of the yolks without cooking them. Once all the milk is incorporated, pour the mixture back into the saucepan.
4. 4Return the saucepan to a low-medium heat. Stir constantly with a wooden spoon or heatproof spatula, making sure to scrape the bottom and sides of the pan. Cook until the custard thickens enough to coat the back of the spoon — when you draw your finger across the back of the spoon, the line should hold cleanly. This will take roughly 8–10 minutes. Do not let it boil or the eggs will curdle. Remove from the heat immediately once thickened.
5. 5Remove the vanilla pod shreds from the custard. Pour the finished custard into a large measuring jug to gauge the volume, then divide it equally between two clean bowls. Each portion should be roughly 1 pint. Label one bowl 'green portion' and one bowl 'almond portion' so you can keep track.
6. 6To the first custard portion (the green portion), add a few drops of vanilla essence and ¼ pint of orange-flower water. Stir well to combine. Add a small amount of apple green food colouring and stir — aim for a soft, muted green similar to the colour of pistachio nuts. Add the colouring gradually, a drop at a time, until you reach the right shade. Do not over-colour; it should be pale and natural-looking.
7. 7Pass the green custard portion through a fine-mesh sieve into a clean bowl, pressing gently with a spoon. This process — historically called 'tammying', which referred to straining through a tammy cloth — removes any lumps or vanilla pod fragments and gives the custard a silky-smooth texture. Discard any solids left in the sieve.
8. 8Pour the strained green custard into a freezer-safe container or into an ice cream machine if you have one. If using a machine, churn according to the manufacturer's instructions until partly frozen — the mixture should be thick, slushy, and hold its shape when stirred but not yet fully set. If using a freezer, pour into a shallow container and freeze for about 1–1½ hours, stirring vigorously every 30 minutes, until it reaches a thick, softly frozen consistency.
9. 9In a clean bowl, whip ½ pint of cream until it forms soft peaks. Add half a teaspoon of castor sugar and fold it gently through the cream. Once the green custard is partly frozen (thick and slushy but not solid), remove it from the freezer or ice cream machine. Gently fold the sweetened whipped cream through the green custard using a large spoon or spatula, working quickly so it does not melt completely. Return to the freezer or churn briefly until just combined and softly set. Set aside.
10. 10Place a sauté pan or wide frying pan over a medium heat. Add half an ounce of butter and let it melt. Add 3 ounces of blanched sweet almonds and 1 ounce of castor sugar. Stir constantly with a wooden spoon. The sugar will melt and begin to caramelise around the almonds. Continue cooking and stirring until the almonds are coated in a deep brown caramel — they should be a rich dark gold. Watch carefully as the caramel can burn quickly. Remove from the heat as soon as they are a deep brown. Tip them out immediately onto a sheet of baking paper and leave to cool completely.
11. 11Once the caramelised almonds are fully cooled and hard, break them into rough pieces. Place them in a food processor and blitz until they form a smooth, paste-like texture — this is a praline paste. Alternatively, place them in a zip-lock bag and crush with a rolling pin, then use a mortar and pestle to grind to a paste. The original recipe calls for pounding in a mortar until smooth; work quickly so the warmth of your hands does not cause the caramel to stick.
12. 12Take the second custard portion (the almond portion) from step 5. Stir the ground caramelised almond paste thoroughly into this custard until fully combined and smooth. The paste will give the custard a rich, nutty, praline flavour.