Black Cocoa Gem Cookies
Initially, this was intended to be Hextech shard (from League of Legends Arcane) black cocoa cookies, but the rock candy I tried making ended up green. So I opted for something somewhat similar and just used blue candy/sprinkles.
If you want use rock candy, maybe try adding tonic water instead of water so that it glows under black/uv light. Blue pop rocks could be interesting as well (don't try making it yourself because it won't be satisfactory), or even blue kohakutou crystals.
Supplies
Ingredients (makes ~11 cookies):
6 tbsp (85 grams) butter, softened (I used margarine because it's soft from the fridge)
½ cup (100 grams) white sugar
2 tbsp (25 grams) brown sugar
1 egg (a flax egg could work here but I haven't tried it; 1 tbsp ground flax with 3 tbsp water)
1 tsp vanilla extract
1 cup (120 grams) all-purpose flour
½ cup (50 grams) black cocoa powder (I got mine from Bulk Barn for ~ $4.3/100g CAD)
½ tsp baking soda
¼ tsp baking powder
½ tsp salt
½ tsp espresso or instant coffee powder (optional, enhances flavor)
Blue candy/gummies or sprinkles
Preheat oven to 350°F (175°C). (Personally, I wait until I am almost done with the recipe because I take longer to make things) Prepare 1 baking sheet with parchment paper or a silicone mat.
Cream butter and sugars. Add egg and vanilla.
Mix flour, black cocoa, baking soda, baking powder, salt, espresso; add to wet ingredients. (Or just add directly to wet ingredients like I did)
Scoop dough into ~11 small balls onto baking sheet, leaving ~2 inches space in between. Roll in blue sprinkles or leave as is if using candy pieces. Flatten slightly.
Bake 12-14 min at 350°F. Remove from oven and let cool. If you choose to do so, press a few candy shards/gummy pieces onto each cookie while it's warm.