Rustic French Almond Puff Pastry Galette

Place softened unsalted butter and granulated sugar into a medium mixing bowl. Cream together using a silicone spatula or whisk for 2 minutes until pale, smooth, and evenly blended.

Add 1 room temperature beaten egg, dark rum, and pure vanilla extract to the creamed butter mixture. Beat thoroughly with a whisk for 1 minute until fully emulsified.

Add blanched almond flour, cornstarch, and fine sea salt to the bowl. Fold gently with a silicone spatula just until dry ingredients are fully incorporated and no pockets of almond flour remain.

Cover the almond filling bowl with plastic wrap and chill in the refrigerator for 15 minutes to firm the butterfat.

Preheat your oven to 200°C (400°F) with a rack positioned in the lower-middle tier. Line a heavy baking sheet with parchment paper.

Dust a clean work surface lightly with flour. Roll out both portions of chilled puff pastry with a rolling pin into two equal circles measuring 23 cm (9 inches) in diameter and approximately 3 mm thick.

Transfer one pastry disc onto the prepared parchment-lined baking sheet. Spoon the chilled almond filling into the center and spread it into an even layer using an offset spatula, leaving a clear 3 cm perimeter border along the edges.

Whisk the second egg with 5 ml water in a small cup to make egg wash. Using a pastry brush, lightly paint the exposed 3 cm perimeter border of the bottom pastry disc, taking care not to let egg wash drip over the cut edge.

Drape the second pastry circle squarely over the almond filling. Press gently along the border with your fingertips starting from the inside edge outward to push out any trapped air bubbles, then crimp the outer perimeter by pressing lightly with the back spine of a paring knife at 1 cm intervals.

Transfer the baking sheet with the assembled tart into the refrigerator to chill for 20 minutes to firm the laminated butter in the pastry before baking.

Brush the top surface of the tart evenly with the remaining egg wash, avoiding the outer cut edge. Using the tip of a sharp paring knife, cut a 3 mm vent hole in the very center, score curved spiral rays across the top pastry without cutting all the way through, and scatter sliced almonds over the center.

Transfer the baking sheet to the lower-middle rack of the oven. Bake at 200°C (400°F) for 20 minutes until the pastry is puffed and golden, then reduce heat to 180°C (355°F) and continue baking for 20 to 25 minutes until the pastry is deeply caramelized and an instant-read thermometer inserted into the center reads at least 71°C (160°F).

Remove the baking sheet from the oven. Slide the tart together with the parchment paper onto a wire cooling rack and allow it to cool undisturbed for at least 30 minutes so the frangipane sets.

Transfer the tart to a cutting board and slice into 8 equal portions using a sharp serrated knife with gentle sawing motions to prevent crushing the flaky layers.