Limoncello Mousse Tart Recipe

Preheat oven to 350°F (175°C). In a medium bowl combine graham cracker crumbs, granulated sugar, salt and lemon zest and stir to evenly distribute.

Pour melted butter over crumbs and stir until mixture resembles wet sand and holds together when pressed. Press mixture evenly into a 9-inch tart pan with removable bottom (or into a 9-inch tart tin), pressing firmly up the sides to form an even 1/4–1/2-inch-thick shell.

Bake crust 10–12 minutes until set and fragrant. Remove from oven and cool on a rack. Leave oven on if you will reheat briefly later, otherwise allow crust to cool fully to room temperature before filling.

In a heatproof bowl whisk together egg yolks, whole egg and granulated sugar until smooth and slightly pale.

Stir in lemon juice, lemon zest and salt until combined.

Set the bowl over a pot of simmering water (double boiler), ensuring the bottom of the bowl does not touch the simmering water. Whisk constantly until mixture thickens and registers about 170–175°F (77–80°C) or coats the back of a spoon, about 8–12 minutes.

Remove bowl from heat and immediately whisk in cold cubed butter, a few pieces at a time, until fully incorporated and the curd is smooth and glossy. Stir in limoncello. Taste and adjust salt or lemon if needed.

Transfer curd to a clean container. If using the curd both as base filling and reserved for folding into mousse, divide: set aside 1 cup of curd at room temperature for the mousse; pour the remaining curd into the cooled tart crust to make a 1/2–3/4" layer. Smooth the surface. Chill the tart with curd in the refrigerator to set while you prepare the mousse (about 30 minutes). Reserve the 1 cup of curd for the mousse.

Bloom the gelatin: sprinkle powdered gelatin over 2 tablespoons cold water in a small bowl and let sit 5 minutes until spongy.

Warm the bloomed gelatin gently in the microwave for 5–10 seconds or over a warm water bath until liquid (do not boil). Let cool slightly but keep fluid.

In a chilled mixing bowl whip the cold heavy cream with powdered sugar and vanilla to soft-medium peaks. Do not overbeat; you want a smooth stable cream.

Whisk the reserved 1 cup lemon curd until loose. Whisk a tablespoon of whipped cream into the warm gelatin to temper it, then whisk that into the lemon curd to evenly combine.

Fold about one-third of the whipped cream into the curd to lighten it, then gently fold in the remaining whipped cream until homogeneous and airy. Taste; if you prefer a stronger limoncello note, gently fold in the optional extra limoncello (use sparingly to avoid breaking the mousse).

Spoon or pipe the limoncello mousse over the chilled curd layer in the tart, smoothing the top. Chill the assembled tart at least 2 hours (preferably 3–4 hours) until mousse is set.

Preheat oven to 325°F (160°C) or use the oven you already had on. On a small rimmed baking sheet toss pistachios with honey and butter until evenly coated; spread in a single layer. Roast 8–10 minutes until fragrant and just beginning to color, stirring once halfway. Watch closely to prevent burning.

Remove from oven, sprinkle with salt, let cool, then roughly chop. Keep at room temperature until ready to garnish.

Set a heatproof bowl over a pot of simmering water (double boiler). Add egg whites and granulated sugar (and cream of tartar if using) to the bowl. Whisk constantly until the sugar dissolves and the mixture reaches 160°F (70°C) or feels warm and the sugar is dissolved (about 3–4 minutes).

Remove bowl from heat and transfer to a stand mixer fitted with the whisk attachment (or use a handheld mixer). Whisk on medium-high until the meringue forms glossy stiff peaks and the bowl is cool to the touch, about 6–8 minutes. Add vanilla extract in the last minute and whip to incorporate.

Immediately spread or pipe the Swiss meringue over the chilled mousse-topped tart in an even layer or decorative peaks, covering the mousse completely.

Using a culinary torch, carefully brown the meringue to desired color, moving the flame continuously to avoid burning. If you don't have a torch, briefly place under a very hot broiler for 30–60 seconds watching constantly (may soften mousse).

Brush the exposed edges of the crust or the meringue margin very lightly with 1 tablespoon limoncello if desired for aroma (optional).

Scatter the honey-roasted pistachios over the browned meringue or around the tart edge, and finish with microplane lemon zest.

Return tart to refrigerator for 10–15 minutes if the meringue melted slightly, then slice with a hot dry knife (wipe between cuts) and serve chilled. Store refrigerated up to 2–3 days; meringue is best eaten the same day.