Blitz 100 grams of mini pretzels in a food processor to a very fine crumb with minimal chunks. Use the crumbs for the entire recipe.
Make the crust: Whisk the all-purpose flour, pretzel crumbs, sugar, and salt in a large bowl until combined. Add the cold butter, and toss with your hands to coat the cubes in flour. Press each piece of butter, one at a time, in-between your fingers, and then drop them back into the flour mixture. Toss again with your hands to coat the butter in the flour. The butter pieces should be thin, flat shards.
Add the ice cold water, 2 or 3 tablespoons at a time, gently mixing with your hands after each addition, to form a shaggy and crumbly dough that sticks together when pressed with your hands. The amount of water needed will vary.
Transfer the dough to a sheet of plastic wrap, and use the plastic wrap to press the dough into a ¾ inch thick disc. Refrigerate for at least 1 hour or up to 24 hours.
Meanwhile, make the frangipane. Using an electric or stand mixer fitter with a paddle attachment on medium, cream the butter and sugar together until light and fluffy. Beat in the egg until smooth, and scrape down the bowl with a spatula. Add the almond flour, pretzel crumbs, vanilla, salt, and almond extract. Mix on low to combine.
Add the blueberries, sugar, cornstarch, and salt to a large bowl, and toss to combine.
Preheat oven to 425° F. Line a baking sheet with parchment paper.
On a floured work surface, roll out the chilled dough to form a rough 15-inch circle, dusting the dough and work surface with flour as needed. If the dough is too firm from the refrigerator and starts to crack while rolling, let it sit at room temperature for 5 to 10 minutes before proceeding. Rotate and flip the dough to help with sticking. If the dough tears, gently press it back together. Transfer the dough to the baking sheet.
Add the frangipane to the center of the crust, and use an offset spatula to spread it out, leaving a 4-inch border. Pile the blueberry mixture on top of the frangipane, leaving the 4-inch border bare.
Fold the untouched edges of the crust over the blueberries to form the galette. Chill the galette in the freezer for 10 minutes or in the refrigerator for 20 minutes.
While the galette chills, whisk one egg and 1 tablespoon water to form the egg wash. Brush the crust all over with the egg wash, and sprinkle on the mini pretzels and raw sugar.
Bake for 45 to 55 minutes, until the blueberries are bubbly and the crust is a deep golden brown.
Meanwhile, make the cream cheese whip. Using an electric or stand mixer fitted with a whip attachment on medium, whip the cream, cream cheese, sugar, vanilla, and salt to form very soft peaks, about 4 minutes. Transfer to the refrigerator to chill until ready to serve.
Let the galette cool for at least 20 minutes before serving. Serve warm or at room temperature with the chilled cream cheese whip on the side.