Iced Biscuit Mont-Blanc

Ingredients

Equipment Needed

• •Straight-sided 9 x 5-inch (23 x 13 cm) metal loaf tin
• •Fine-mesh sieve or tamis
• •Stand mixer or electric hand mixer
• •Small heavy saucepan
• •Sugar or instant-read thermometer
• •Digital kitchen scale
• •Flexible silicone scraper

Instructions

1. 1

   Prepare mold and chestnut

   Line a straight-sided 9 x 5-inch (23 x 13 cm) loaf tin with plastic wrap, smoothing it firmly into the corners and leaving enough overhang to lift the dessert out upright. Chill the tin. Stir 1 tablespoon of the reserved cream into the chestnut purée, then force it through a tamis, a very fine sieve, with a flexible scraper. If it bunches against the mesh, add the second reserved tablespoon of cream and warm the bowl briefly over barely warm water. Any unused reserved cream goes into the sieved purée. This step stays: chestnut fibers freeze into cords that catch the serving knife, while a fine purée gives a clean, creamy middle.

2. 2

   Whip the cream softly

   Whip the remaining cold cream until it forms soft peaks whose tips bend over. Stop while it still looks smooth and supple. Stiff cream is difficult to fold and leaves the frozen biscuit crumbly rather than close and creamy. Keep it covered in the refrigerator while you make the egg foundation.

3. 3

   Make the pâte à bombe

   Put the yolks and salt in the mixer bowl. Combine the sugar and water in a small heavy saucepan, stir over gentle heat only until the sugar dissolves, then boil without stirring. When the syrup reaches 230°F (110°C), begin whisking the yolks at medium speed. At 244°F (118°C), remove the syrup from the heat and pour it in a thin stream down the inside of the bowl, never directly onto the moving whisk. Increase the speed and beat for 6 to 8 minutes, until the pâte à bombe, the hot-syrup egg-yolk foam, is pale, tripled in volume, and no longer warm. If the syrup crystallizes in the pan, add 1 tablespoon of water, dissolve it gently, and bring it back to temperature.

4. 4

   Divide the foundation

   Weigh the pâte à bombe and divide it among three bowls in a 3:2:3 ratio, labeling them rum, chestnut, and vanilla. Divide the whipped cream by weight in the same ratio. The chestnut portion is deliberately smaller because the purée supplies the missing volume; once flavored, all three preparations will fill roughly equal thirds of the mold. Cover and refrigerate the chestnut and vanilla portions while the rum layer sets.

5. 5

   Set the rum base

   Stir the dark rum into its portion of pâte à bombe. Fold in one-third of the corresponding whipped cream to loosen it, then fold in the rest with broad strokes, preserving as much air as possible. Spread the rum preparation across the bottom of the chilled mold and level it without pressing. Freeze for 30 to 40 minutes, until the surface is firm under a light fingertip but remains slightly tacky. Rum slows freezing, so give it another 10 minutes if the surface still yields wetly.

6. 6

   Build the chestnut middle

   Whisk one-third of the chestnut portion of pâte à bombe into the sieved purée until perfectly smooth, then fold in the remaining pâte à bombe and its allotted whipped cream. Spoon or pipe the chestnut preparation gently over the rum base, working from the edges inward so the lower layer isn't disturbed. If the first spoonful sinks, stop, lift away only that spoonful, and freeze the rum layer for another 10 minutes. Ça se rattrape. Level the chestnut and freeze for 30 to 40 minutes, until firm enough to support the final layer.

7. 7

   Finish with vanilla

   Stir the scraped vanilla seeds into the final portion of pâte à bombe, then fold in its whipped cream as before. Spread the vanilla preparation over the set chestnut layer, filling the mold to the top and smoothing it cleanly. Fold the plastic overhang loosely above the surface without pressing against it, cover the tin, and freeze for at least 6 hours, preferably overnight.

8. 8

   Unmold and slice

   Let the biscuit glacé stand at room temperature for 5 minutes. Open the plastic wrap and lift the loaf straight from the mold so the rum remains at the base and the vanilla at the top. If it clings, wrap the outside of the tin in a warm damp towel for 5 seconds and try again. Peel away the lining, then cut 8 generous slices with a knife warmed in hot water and wiped completely dry between cuts. Serve at once. À table!

Chef Tips

• •Buy unsweetened chestnut purée, which contains chestnuts and little else. Crème de marrons is already heavily sweetened and often vanilla scented; it changes the freezing point, obscures the three flavors, and isn't an equal substitution.
• •Use an unspiced dark rum with a rounded molasses character. Keep to the measured amount. More rum may sound festive, but alcohol softens frozen mixtures, and an enthusiastic pour leaves the bottom layer slumped on the platter.
• •A freezer holding 0°F (-18°C) gives the cleanest layers. If yours runs warmer, allow another 15 minutes between preparations and freeze the completed mold overnight.
• •Warm the knife, then wipe it dry before every cut. Heat passes through the frozen cream cleanly, while water left on the blade forms icy streaks against the chestnut.

Advance Preparation

• •Make the complete biscuit glacé 1 to 3 days before serving. Keep it covered in its mold so the surface doesn't pick up freezer odors or frost.
• •The chestnut purée can be sieved a day ahead and refrigerated in a covered container. Let it return to room temperature before folding so it doesn't tighten the pâte à bombe.
• •Unmold only when the platter, knife, and guests are ready. Once sliced, return any remaining biscuit glacé to the freezer promptly, well wrapped.

Frequently Asked Questions

Nutrition Information

1 serving (about 120g)