They're surprisingly simple to make though the small size of the trays make them a bit tough to work with. Feel free to use larger silicone ice cube trays if you can find them.
I wanted opaque skulls and decided to use a Jello cheesecake pudding for the color/flavor, and Knox gelatin for the jelling. You can use any white pudding- vanilla, white chocolate, or cheesecake. For both ice cube trays (1 pumpkin, 1 skulls) I guessed that I'd only need half a package of pudding. For once, I was exactly right. I was left with very little leftover.
To begin, make half a batch of jello pudding (mine was ½ box and 1 cup cold milk). If you don't have a scale to be precise, make up the whole batch and eat half. I won't tell anyone. ;)
Now grab your silicone trays. Lightly spray with cooking spray or lightly wipe with a bit of canola/ vegetable oil. Very very lightly!
Go fold a load of laundry, enjoy a glass of wine, or watch a couple funny YouTube videos. I'll wait.
(Well, kind of. I'm not a patient person. So while I was waiting for the skulls to set up, I set aside a small amount of the white mix and made the pumpkins with the remaining pudding/gelatin- details to follow after the skulls.)
Skulls all jellied? Great. Time to move on. Use a tiny spoon to scoop out a tiny bit of skull. Baby spoons work great here! Make sure you don't take too much out of the mold or you'll be able to see the "brains" and they'll leak out.
Fill the void with a tiny bit of raspberry jam. Don't overfill them.
Now take the remaining gelatin/pudding and fill the molds the rest of the way. If it's too thick, microwave for 5-10 seconds.
To make the pumpkins, tint a small amount of the pudding mixture green and use a toothpick to put it in the stem spot.
Remove the trays from the freezer, fill with orange gelatin/pudding, return to freezer until frozen, pop out and store the same as the skulls.