In a bowl, add the flour. Take the cold butter straight from the fridge, coat it lightly in the flour, then grate it on the large holes of a box grater directly into the bowl with the flour.
Add the baking powder, salt, sugar, cottage cheese and the egg to the bowl.
Knead the dough with your hands until it comes together, then shape it into a ball of dough. Wrap the dough ball in plastic wrap and refrigerate it for about 30 minutes.
After the resting time, take the dough out of the fridge and place it on a sheet of parchment paper. Roll the dough out with a rolling pin into a roughly round sheet.
Slice the strawberries in half and toss them with the sugar and cornstarch until evenly coated.
Arrange the strawberries in the center of the rolled‑out dough, then gently fold and pleat the edges of the dough up over the fruit, leaving the middle exposed.
Bake in a preheated oven at 350 °F (180 °C) for 35–40 minutes, until the crust is golden and the filling is bubbly.
Let the galette cool completely before slicing so the filling can set and not run out. Just before serving, dust the top with powdered sugar.