1 cup (226g)unsalted butter softened to room temperature
⅓cup (70g)sugar
⅓cup (70g)light brown sugartightly packed
1largeegg yolk
¾tspvanilla extract
2 ¼cup (280g)all purpose flour
2tspcorn starch
½tsp salt
½cupsugarfor rolling
⅓cup (105g)raspberry jelly
Instructions
Place butter in the bowl of a stand mixer (you may instead use a large bowl and an electric hand mixer) and beat until creamy.
Scrape down the sides of the bowl, add sugars, and beat, gradually increasing mixer speed to medium-high until ingredients are well-combined (about 30-60 seconds).
Add egg yolk and vanilla extract and beat well.
In a separate bowl, whisk together flour, cornstarch, and salt.
With mixer on low speed, gradually add flour mixture to wet ingredients until completely combined.
Scoop cookie dough into 1 Tablespoon-sized balls and roll very well (so that the dough is round and there are no cracks/seams in the cookie dough — this will help keep your thumbprints from cracking). Roll balls in granulated sugar (if using) and place on a wax-paper covered plate or small cookie sheet. Use your thumb or the rounded back of a teaspoon to gently press an indent in the center of the cookie dough. Repeat until all of the dough has been used.
Transfer cookie dough to freezer and chill for 30 minutes.
Preheat oven to 375F (190C).
Place cookies (at least 2″ apart) on a parchment paper-lined cookie sheet and bake on 375F (190C) for 11 minutes or until edges are just beginning to turn golden brown.
Place a teaspoon of jam in the center of each thumbprint.
Add a piece of Fiber 1 to the top of the jam.
Shape fondant into a small leaf and place it near the "stem".