Choux Buns with Caramel and Pistachio

Name: Choux Buns with Caramel and Pistachio
Cuisine: French
Ingredients: 240 milliliters whole milk (1 cup); 50 grams granulated sugar (1/4 cup), divided; 60 grams egg yolks (about 3 large yolks); 15 grams all purpose flour (1 tablespoon + 1 teaspoon); 15 grams cornflour/cornstarch (2 tablespoons); 1 teaspoon vanilla bean paste; 60 milliliters water (1/4 cup); 60 milliliters whole milk (1/4 cup); 45 grams unsalted butter (3 tablespoons), plus more to prepare the tray; 1/2 teaspoon kosher salt; 1/2 teaspoon granulated sugar; 75 grams all purpose flour (1/2 cup + 1 tablespoon), sifted; 125 grams whole eggs, beaten (about 2 large eggs); 1 egg, for egg wash; 105 grams granulated sugar (1/2 cup); 45 milliliters water (3 tablespoons); 20 grams light corn syrup or liquid glucose (1 tablespoon); 1/2 teaspoon fine sea salt, optional; 30 grams crushed pistachios (3 tablespoons)