In the bowl of a food processor fitted with blade attachment, pulse together flour, sugar, and Kosher salt. Add cold butter and shortening, then pulse until small, pea-sized pieces form. Add ice water, then pulse, adding the last tablespoon as needed, until the dough begins to come together.
Dump the dough out onto a sheet of plastic wrap and roll into a flat disk. Chill. If you leave the dough in the fridge longer, it may need to sit out at room temperature until it is easier to roll out.
Place granulated sugar in a large mixing bowl. Zest a lemon directly on top , then use your fingers to rub the zest into the sugar. Add sliced strawberries, cornstarch, and a pinch of Kosher salt. Use a spatula to stir well.
On a lightly floured surface, use a rolling pin to roll out the chilled pie dough into a round. Doesn’t have to be perfect, galettes are rustic! Carefully transfer to a baking sheet lined with parchment or Silpat.
Use a spatula to spread the frangipane all over the pie dough, leaving a 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. Press down slightly to seal.
In a small bowl, whisk together 1 large egg and 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.
Refrigerate. When ready, preheat an oven to 400F.
Bake until the crust is golden brown and the strawberries are bubbling.
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!