Preheat your oven to 400°F. While the oven heats, hull and slice the strawberries into 1/4-inch thick pieces, then trim the rhubarb stalks and cut them into 1/2-inch slices. This prep work ensures you're ready to move quickly once cooking begins, and having everything measured and ready prevents any rushed moments during the galette assembly.

Combine the sliced strawberries, rhubarb, sugar, lemon juice, vanilla extract, salt, and cornstarch in a skillet over medium-low heat. Cook for 6-7 minutes, stirring occasionally, until the fruit softens and the mixture thickens slightly—the cornstarch will absorb excess moisture and prevent a soggy bottom crust. I like to taste the filling at this point and add a bit more lemon juice if needed to brighten the sweetness of the rhubarb. Transfer the filling to a bowl and let it cool slightly while you prepare the pastry.

Whisk together the egg and water in a small bowl to create the egg wash—this will give the pastry its beautiful golden color. Unroll the puff pastry sheet onto a piece of parchment paper. Gently trim it into a rough oval shape using a sharp knife, leaving about a 2-inch border around the edges for folding. Using a fork, poke holes across the center of the pastry (avoiding the border area) to prevent the bottom from puffing up too much during baking.

Spoon the cooled fruit filling from Step 2 into the center of the prepared pastry, leaving a 2-inch border of exposed dough all around. Fold the edges of the pastry up and over the filling, allowing the edges to naturally crease and fold—the galette should have a rustic, free-form appearance. Brush the exposed pastry border generously with the egg wash from Step 3, making sure to coat all the folded edges for an even, glossy finish.

Transfer the parchment paper with the galette directly onto a baking sheet, then place in the preheated 400°F oven. Bake for 18-23 minutes until the pastry is puffed and deeply golden brown. Remove from the oven and let the galette cool on the baking sheet for 10-15 minutes—this resting time allows the filling to set slightly so it won't leak when you slice it. I find that waiting this extra time makes a huge difference in presentation and keeps the galette from falling apart.

Slice the galette into wedges and serve while still warm. Top each slice with a generous scoop of vanilla ice cream, which will melt beautifully into the warm fruit filling and create a delicious contrast of temperatures and textures.