In a large bowl, whisk together almond flour, baking soda and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, cream together sugar and butter at medium speed until fluffy and granular, 2-3 minutes. Add egg and vanilla and mix until smooth. Add sour cream and mix until smooth. Add dry ingredients and mix to combine.
If scooping dough, tightly cover mixing bowl and refrigerate 2 hours or overnight. If rolling out and cutting dough, transfer to a large piece of plastic wrap on a work surface and wrap to cover dough completely, shaping into a 1-inch thick disc. Place in freezer for 2 hours - you want the dough to be as cold as possible, but still pliable.
When ready to bake:
Preheat the oven to 350˚F.
Line a baking sheet with parchment paper.
To Scoop, Flatten and Bake (easiest method):
Fold a piece of plastic wrap into a ~3-inch square (to prevent drinking glass sticking to dough).
Scoop dough out into 2-tablespoon balls (this cookie scoop is ideal) and place on baking sheet, leaving 2 inches between each ball. Place plastic wrap on dough ball and flatten with a wide bottomed drinking glass, ½-inch thick for soft cookies or ¼-inch thick for crispy cookies. Repeat with remaining balls. (There should be at least an inch between each cookie when they're all flattened.) Sprinkle cookies generously with sparkling sugar if desired. (You can gently press sugar in with the bottom of the drinking glass or your fingers to ensure that it adheres.)
Bake 9 to 12 minutes for thick and soft cookies, 10 to 14 minutes for thin and crispy cookies. (recipe note #2) Transfer baking sheet to wire rack and let cool for a few minutes before carefully transferring cookies directly to rack to cool completely.
To Roll Out, Cut and Bake
Generously sprinkle almond flour on work surface. Place dough disc in center and sprinkle generously with almond flour. Working quickly, roll dough into a ¼" thick circle. Cut with 3-inch round cookie cutter; remove dough scraps around cookies. With dough scraper or thin metal spatula, carefully transfer to prepared baking sheet leaving at least 1" between cookies as they'll puff and spread. Sprinkle with sparkling sugar if desired (gently press sugar into each cookie with your fingers to make sure it adheres). If desired, gather dough scraps into a disc; roll and repeat process.
Bake 9 to 12 minutes for soft cookies, 10 to 14 minutes for thin, crispy cookies. Transfer baking sheet to wire rack and let cool for a few minutes before carefully transferring cookies directly to rack to cool completely.
The thin crispy cookies will stay crisp at room temperature for a few days. However, the thick soft cookies are best eaten the day they're baked. Overnight they get chewier (more like the texture of a macaroon), though still quite tasty. To avoid this, scoop and flatten the dough on a baking sheet, sprinkle on sugar (press to adhere), and transfer to freezer until solid. Once frozen, transfer dough discs to a freezer safe plastic bag in single layers separating each layer with parchment paper. To bake, arrange frozen discs 1-inch apart on baking sheet and add let thaw at room temperature while you preheat your oven (15-20 minutes). Or, the day before you plan to bake, arrange frozen discs on baking sheet. Cover and let thaw in the refrigerator overnight and bake as recipe directs.
Note that cook time is the maximum per batch so will be longer if you bake multiple batches in a single day.