Does "very thick" mean nothing to you?

So... Treacle?

When does something count as being eaten - once you swallow it? I don't think you'd succeed at that with lava.

Just shove an insulated hose through your esophagus and out your bunhole and pass lava through it

In fact, lava is so nutritious it will fill you up for the rest of your life!

I choose to believe you're taking about having pica, not eating a molten chocolate cake.

Alright so I got curious. For the non people-who-know-what-viscosity-is-measured-in people out there, viscosity is measured in centipoise, which is 1/100 poise. Water is 1 centipoise, hence why we use centipoise over poise. Don't ask me any more than that because I have no idea what I'm talking about.

Lava is anywhere between 10,000 - 1,000,000 cP. According to this chart, there are many edible things that fall within that viscosity. Now lava is very hot, so if we're going to simulate the experience of eating lava in a safe way with edible ingredients, we need something that is that viscous at high temperatures. This page (PDF warning) says that 140f (60c) is the highest temp food can be without burning you immediately.

There isn't much on the above chart that is both edible and has its viscosity measured around those temps. The most promising one was chocolate, which is about 25,000 cP. But it doesn't have a temperature listed. According to lived experience and my ass, melted chocolate has a pretty consistent viscosity at various temperatures, making it a suitable stand in for molten lava.

However, viscosity isn't the end all be all of a lava eating experience. Lava is rocks and rocks are dense. Lava also looks like it would be sticky. Unfortunately, I couldn't find anything on the chart that matches the density of lava that is still edible (2600-2800 kg/m^3 for those who were curious). And there is also no unit of measurement for stickiness. But google tells me that some lava is sticky like peanut butter. So our edible lava needs to be considerably dense (thus, chewy) and sticky.

With these things in mind (viscosity, chewiness, and stickiness), I think the best edible stand ins for molten lava would be hot peanut butter (250,000 cP), with honorable mentions being rice pudding (10,000 cP @100C), and hot toothpaste (70,000 cP @40C). Color them bright orange and maybe throw in some Carolina reaper for authenticity and baby you've got some edible lava going

Yeah. You know all those is movies and stuff where people sink in lava?

Nope. It's too dense. You'd be so buoyant you'd just stay on top.

Gate to be the party pooper but lava is specifically molten rock, and rock is a mixture of multiple minerals. As single mineral is not rock. (As far as a quick Google is verifying, open to correction by an expert)

New headcanon is lava has the consistency of cheese sticks

Yeah but salt is rocks and that stuff is delicious

Yeah, but since it's a liquid it doesn't have the texture of solid rock.

It's gotta be pahoehoe (the one that looks like honey being stirred)

'a'ā looks like it would fizz like pop rocks.

Imagine the terminology if instead of it coming from the study of the Hawaiian volcano system, it came from the Icelandic one.
Then we'd be memorizing words like herliaphongoffjlyur.

I dunno, eating implies swallowing, I'm not convinced you could definitely get there.