Add onions to a mini prep food processor and pulse until course crumbs are formed. Add sesame seeds, poppy seeds, and garlic powder and pulse to incorporate. Set aside.
Deviled Egg filling
Add onions and oil to a small skillet and sauté until soft and beginning to brown, ~4 minutes. Turn off heat and add grated garlic, stir to incorporate, letting the residual heat cook the garlic.
Into a food processor, add egg yolks, cream cheese, sour cream, onion mixture and blend until smooth. Add cheese, salt, pepper, and mustard and blend to incorporate. If mixture is too dry, add a little more sour cream. The mixture should have the consistency of hummus. Taste and adjust seasonings as needed.
Transfer mixture into a piping bag and pipe mixture into two skull molds, use a spatula to work the mixture into the mold and smooth over the mold. Place molds in freezer for about 15 minutes. Remove from freezer and use the spatula to press down on the chilled mixture to ensure the mold leaves a good skull impression and place back into the freezer for another 20 minutes before plating your deviled eggs.
Place edible soil onto your serving plater and place the egg whites on it. Pipe a small amount of filling into each egg white and top with a frozen skull mixture. Garnish with dill and edible flowers and serve. Feel free to add tombstones like I did to add that extra spooky touch.
Notes
You can get edible flowers from https://gourmetsweetbotanicals.com/Mini Skull ice mold from AmazonMini Skull molds from this shop on Etsy. (Not sure if this shop is still open)I got these mini chalkboard tombstones from Michael's many years ago, but you can look online for something similar.I used stickers to mask RIP and then sprayed them with gray paint, then removed the stickers and aged it and added cracks with a little black stencil paint.