2 1/2 cups tapioca flour/starch
1 egg yolk
1 cup powdered sugar
1 tablespoon butter, melted
1/2 cup (120 ml) coconut milk/cream
Place the tapioca flour in a bowl and microwave it for 1 minute (to get rid of any excess moisture). Let it cool. Pour it into a mixing bowl and mix in the powdered sugar. Then add the egg yolk, butter, and coconut milk. Mix until a dough forms (it has a plastic-y texture that reminds me of mozzarella cheese).
Preheat the oven to 350ºF. Take 1/4 of the dough and place it between two sheets of plastic wrap. Roll the dough out very thinly, 2-3 mm in thickness. For large sand dollars, use a 2 5/8 inch diameter circle cookie cutter, and for small sand dollars, use a 1 7/8 inch diameter circle cookie cutter to cut out circles. Transfer them to a parchment lined baking sheet. Use a toothpick to poke a hole in the center of each circle cut out. Repeat with the rest of your dough.
For the large sand dollar cookies, you'll need a pearl milk tea straw and a regular drinking straw (like the ones at fast food places). For the small sand dollar cookies, you'll need a regular drinking straw and a smaller straw (like a striped bendy straw). Take a pair of clean scissors and cut off a 1 cm piece from the ends of the straws that you are using. Pinch the straw pieces so that the ends become more elliptical than round.
Then take the larger of the two straws and use it to cut out an oval hole in the bottom center of each circle cut out. Use the smaller straw to cut out 2 smaller ovals on both sides of the large hole. By the way, the holes will shrink while they bake, so it's better to make them a bit wider now. Place the cookies in the oven and for the larger cookies, bake them for 6 minutes, and for the smaller cookies, bake them for 5 minutes. At this point, remove the baking sheet from the oven.
Use a toothpick to quickly prick out a dotted five-petaled flower shape on each cookie (be careful not to burn yourself on the baking sheet, if necessary, place an oven mitt on top of the baking sheet edge to have something your arm can rest on). If the middle hole has shrunk, take the toothpick and enlarge it. Place the cookies back in the oven and continue baking until the cookies are relatively crisp and begin to brown at the edges, about 5-7 minutes. Let cool on the baking sheet to finish crisping up, then move to a cooling rack.