In a large mixing bowl, blend the softened butter, sugar, and vanilla extract together until smooth and fully combined.

Slowly add the flour into the butter mixture, stirring well until the dough appears crumbly.

Gently mix the dandelion petals into the dough using a fork.

Transfer the crumbly dough onto plastic wrap and shape it into a log, then wrap it tightly.

Refrigerate the dough for at least 3 hours or overnight.

Unwrap the dough, slice into 1/4-inch thick rounds, and bake at 325°F for 30 minutes.

Let the cookies cool completely and sprinkle with sugar if desired.