Make the galette dough. In the bowl of a food processor fitted with blade attachment, pulse together 2¼ cups (270g) flour, 2 tsp sugar, and ½ tsp Kosher salt. Add ½ cup (113g) cold butter and 7 Tbsp (85g) shortening, then pulse until small, pea-sized pieces form. Add 4 Tbsp (60ml) of ice water, then pulse, adding the last tablespoon (15ml) as needed, until the dough begins to come together.
Chill the pie dough. Dump the dough out onto a sheet of plastic wrap and roll into a flat disk. Chill for at least 30 minutes. If you leave the dough in the fridge longer than that, it may need to sit out at room temperature until it is easier to roll out.
Make the strawberry filling. Place ½ cup (100g) granulated sugar in a large mixing bowl. Zest ½ a lemon directly on top (about 1 tsp lemon zest), then use your fingers to rub the zest into the sugar. Add 1½ lbs (700g) sliced (or quartered) strawberries, 2 Tbsp (15g) cornstarch, and a pinch of Kosher salt. Use a spatula to stir well.
Roll out the pie dough. On a lightly floured surface, use a rolling pin to roll out the chilled pie dough into a 12-inch or 13-inch round. Doesn’t have to be perfect, galettes are rustic! Carefully transfer to a baking sheet lined with parchment or Silpat.
Assemble the galette. Use a spatula to spread the frangipane all over the pie dough, leaving a 2-inch border around the edge clear. Spoon or pour the strawberry filling on top, spreading into an even layer. Gently fold the edges of the dough over the almond and strawberry filling, overlapping until you reach the end. Press down slightly to seal.
Brush with egg wash. In a small bowl, whisk together 1 large egg and 1 Tbsp (15ml) of either heavy cream, milk, or water, then use a silicone pastry brush to brush all over the pie dough. Optional: can sprinkle the pie dough with coarse turbinado sugar, if wanted.
Chill the galette. Refrigerate for 20-30 minutes. When ready, preheat an oven to 400°F / 205°C.
Bake the galette. Bake for 35-38 minutes, or until the crust is golden brown and the strawberries are bubbling.
Cool slightly, then slice. Allow the galette to cool slightly before slicing. Serve with whipped cream, ice cream, or powdered sugar. Can be enjoyed warm or at room temperature!