A classic French dessert featuring a chestnut purée vermicelli mound over a sweet meringue base, topped with whipped cream. This recipe simplifies the traditional method for home cooks.
If using whole chestnuts, score an X on each, boil for 15 minutes, then peel while warm. Alternatively, use pre-peeled cooked chestnuts.
In a saucepan, combine chestnuts, milk, granulated sugar, and vanilla bean (split and scraped). Bring to a simmer, cover, and cook for 20 minutes until chestnuts are very soft. Remove vanilla bean.
Transfer chestnut mixture to a food processor and blend until smooth. Add butter and rum (if using) and process until creamy. Pass through a fine-mesh sieve for extra smoothness. Let cool to room temperature.
In a chilled bowl, whip heavy cream with powdered sugar and vanilla extract until stiff peaks form. Transfer to a piping bag fitted with a star tip.
Place a meringue nest on each serving plate. Pipe a small amount of whipped cream into the center of each nest.
Fit a piping bag with a small plain tip (or use a potato ricer). Fill with chestnut purée. Pipe long thin strands over each meringue, covering the cream completely to resemble a mountain of vermicelli.
Pipe a dollop of whipped cream on top of each Mont Blanc. Dust with cocoa powder or garnish with chocolate shavings. Serve immediately or refrigerate up to 2 hours.
Tips
For a shortcut, use canned chestnut purée (unsweetened) and adjust sugar to taste.
If the chestnut purée is too thick to pipe, thin with a tablespoon of milk or rum.
Meringue nests can be made ahead: bake at 200°F (90°C) for 1 hour, then cool.