Preheat oven to 325 degrees, with racks in upper and lower thirds. In a bowl, whisk together flour, 1/4 cup confectioners' sugar, kosher salt, cinnamon, and ginger. Beat butter with remaining 1/4 cup confectioners' sugar on medium-high speed until light and fluffy, about 3 minutes. Beat in maple syrup and vanilla. Reduce speed to low; gradually beat in flour mixture to combine. Cover bowl; refrigerate until dough is firm but still pliable, about 1 hour (or tightly wrap in plastic and refrigerate up to 3 days).

Roll level tablespoons of dough into balls, then roll in pistachios to evenly coat, pressing nuts into dough to adhere. Transfer to parchment-lined baking sheets, spaced 1 inch apart. Make an indentation in center of each ball with your thumb or the bottom of a thick wooden spoon.

Bake cookies, rotating sheets and rack positions halfway through, until set and golden on bottoms, 18 to 22 minutes. Let cool on sheets 10 minutes, then transfer to a wire rack and let cool completely. Unfilled cookies can be stored in an airtight container at room temperature up to 5 days. To serve, fill center of each cookie with approximately 1/2 teaspoon maple cream and sprinkle with flaky salt.