In the bowl of a food processor, combine the almonds, flour, sugar, and fennel seed. Pulse to finely grind the nuts. Add the extracts and butter to the food processor and continue pulsing until the ingredients combine into a smooth dough (the mixture will be crumbly).
Transfer the dough to a work surface and gather into a ball. Wrap the dough tightly with plastic wrap and chill until firm, about 45 minutes.
Pre-heat the oven to 325ºF. Line two baking sheets with parchment paper and set aside.
Scoop out a piece of dough about 1 tablespoon in size and roll it into a ball. Place the ball on the baking sheet and continue with the remaining dough, leaving about 2 inches between each ball.
Bake the cookies until the bottoms are pale golden brown, 20 – 25 minutes, rotating the sheets halfway through baking. As soon as the cookies come out of the oven, gently toss them in the powdered sugar to evenly coat them (NOTE: to get the best coverage, dredge the entire pan of cookies once through and then immediately repeat).
Store the cookies in an airtight container at room temperature for up to 5 days.
OPTIONAL: If you’d rather use another nut (like walnuts or hazelnuts), swap an equal amount of them for the almonds.