Blueberry Jam Mont Blanc Pastry Recipe

Make the dough

In a bowl of a food processor or using a pastry cutter, combine 1.75 cups flour, 0.5 cup confectioners' sugar and 0.25 tsp salt. Pulse or cut in 0.5 cup cold cubed butter until mixture resembles coarse crumbs with some pea-sized pieces remaining.

Bind the dough

Add 1 egg yolk, 1 tbsp cold water and 0.5 tsp vanilla extract. Pulse or gently mix until dough just comes together. Do not overwork — it should form a cohesive mass when pressed.

Chill and rest

Turn dough onto lightly floured surface, press into a flat disk, wrap in plastic and refrigerate for at least 45 minutes (up to 2 days). This keeps gluten relaxed and butter firm for a tender crust.

Blind bake tart shells

Preheat oven to 350°F (175°C). Roll chilled dough on a lightly floured surface to about 1/8 inch (3 mm) thickness. Cut into rounds to fit six 3.5–4 inch tartlet pans or one 9-inch tart pan. Press into pans, trim edges, chill shells in refrigerator 15 minutes. Line shells with parchment and fill with pie weights or dried beans. Bake 12–15 minutes, remove weights and parchment, brush insides with beaten egg wash (1 egg beaten) and return to oven 3–5 minutes until lightly golden. Let cool completely on a rack.

Cook the blueberries

Combine 2 cups blueberries, 0.5 cup granulated sugar, 2 tbsp water and 1 tbsp lemon juice in a medium saucepan over medium heat. Stir occasionally until the berries release juices and the mixture simmers, about 6–8 minutes.

Thicken with pectin

Once simmering, sprinkle in 1 tsp powdered pectin while stirring constantly to avoid lumps. Continue simmering gently for 2–3 minutes until mixture thickens noticeably. If using very ripe fruit and less acid, the pectin helps the jam set quickly.

Cool and adjust

Remove from heat and let cool to room temperature; jam will thicken further as it cools. Taste and, if desired, adjust sweetness with up to 1 tbsp extra sugar. Chill briefly if needed — jam should be spreadable but not runny.

Heat milk

In a small saucepan, warm 1 cup whole milk with 0.5 tsp vanilla extract until it is hot but not boiling—small bubbles will form at the edge. Remove from heat.

Mix yolks and starch

Whisk together 2 egg yolks, 3 tbsp granulated sugar and 1.5 tbsp cornstarch in a bowl until pale and smooth.

Temper and thicken

Slowly whisk about a quarter cup of the hot milk into the yolk mixture to temper, then whisk the tempered yolks back into the saucepan with the remaining milk. Return to medium-low heat and stir constantly until mixture thickens and comes to a gentle boil, about 2–3 minutes. Boil 30 seconds while stirring to activate the cornstarch fully.

Finish and cool

Remove from heat, whisk in 1 tbsp unsalted butter until melted and smooth. Transfer pastry cream to a clean bowl, press plastic wrap directly onto surface to prevent a skin, and chill until cold, at least 1 hour.

Prepare chestnut mixture

In a medium bowl, combine 1.5 cups sweetened chestnut purée, 2 tbsp softened unsalted butter, 2 tbsp heavy cream and 0.5 tsp vanilla extract. Beat with a hand mixer or whisk until smooth and spreadable. Taste and add up to 1 tsp confectioners' sugar if you prefer a sweeter paste.

Pipe into vermicelli

Transfer chestnut paste to a pastry bag fitted with a fine multi-hole Mont Blanc or spaghetti tip (or a #4 round tip). If paste is too stiff, loosen with 1–2 tsp additional heavy cream until it extrudes cleanly.

Fill tart shells

When tart shells and pastry cream are chilled, spoon or pipe about 1 to 1.5 tbsp of pastry cream into each baked tart shell (or spread evenly across a single large tart to about 1/4 inch thickness). Smooth the surface gently.

Add blueberry jam layer

Top the pastry cream with 1 tbsp (for small tartlets) or 3/4 cup (for a 9-inch tart) of the cooled blueberry jam, spreading evenly to the edges of the cream layer. The jam acts as a fruity layer between cream and chestnut strands.

Pipe chestnut vermicelli

Using the prepared pastry bag, pipe concentric rings of chestnut vermicelli over the jam, building up a small dome in the center for each tartlet (about 2–3 tbsp paste per tartlet). For a larger tart, create a low mound in the center or pipe across the whole surface in decorative rows until you’ve used the paste.

Finish and garnish

Lightly dust with powdered sugar, place 1–2 fresh blueberries and a small mint leaf on top of each tartlet center as garnish. For a slight sparkle, sprinkle a scant 1 tsp granulated sugar across tart edges before serving. Chill assembled tarts for 20–30 minutes so layers settle, then serve at cool room temperature.

Storage

Store in an airtight container in the refrigerator up to 2 days (chestnut paste can dry slightly if stored longer). For best texture, consume within 24 hours.