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