Via Memory Alpha:
The Horta was a silicon-based lifeform from Janus VI. It was composed of a material similar to fibrous asbestos.
Now, a delicious main course.
Start by building your Horta’s internal organs. Mince your mushrooms, finely chop your onions, and use the fine grain of your box grater to shred your carrots. Don’t ask which vegetables represent the kidneys. Hortas are a mysterious race.
Add your minced garlic, Worcestershire, salt, pepper, sage, mustard powder, and 1/2 cup of ketchup. You should end up with an organic slurry that still somehow looks like it belongs inside an animated rock. Good job. Now add in the eggs. They act like the cement gluing all your Horta’s parts together. Finally, add in the meat and breadcrumbs.
Knead everything together until your Horta is a uniform, rocky mass.
Arrange the Horta into a half-dome shape. A Horta’s surface is covered in rocky protrusions, so use your fingers to sculpt quarter size knobs across the creature’s surface.
Use both a spoon and your fingers to spread the remaining ketchup into all the sunken crevices of your Horta’s surface. Some dark, round sections should stick up past the red.
Bake the Horta at 400˚ F for 50 minutes.
Before the Horta comes out of the oven, cut your cheddar into thin slices. As soon as it comes out of the oven, carefully arrange the cheese in mineable veins winding through the Horta’s sunken areas. If you use real cheese, it will start melting into the surface quickly (fake, plastic cheese doesn’t change shape.) Use a toothpick to gently blend the cheese into the baked ketchup.
Serve with Romulan Ale, Klingon Blood Wine, or a simple cup of Earl Grey, hot.