I'm posting this for myself as much as for anyone else--I cobbled it together from a couple different recipes and it turned out pretty well so...
1) Take a beef heart, put it on a trivet in the Instant Pot with 1 cup water, cook on high pressure for 30 minutes. When it's done, take it out, slice it, and then run it through the food processor.
2) Dice up a couple onions plus any other veggies you want--peppers would probably be nice but I didn't put any in, just onions. Clean out Instant Pot, add some oil and saute the onions.
3) Take a pound or so of raw liver and run it through the food processor. Add liver and 2 # of ground beef to the instant pot. Add a bunch of salt and pepper and cook, stirring every so often, until it's more or less cooked.
4) Add about a half cup of brewed coffee, 25 oz diced tomatoes, 1 c. beef or chicken broth, 4 T. chili powder, 1 1/2 T cumin, 1 tsp dried coriander, 1 tsp dried oregano, 1-2 T. maple syrup, and 2 T. apple cider vinegar.
5) Cook on high pressure for... an hour I think I did?
See? I'm already forgetting and it's only been 24 hours. That's why I need to write this stuff down.
I got lucky with this, I offered it to my 12-year-old without telling her that it had liver and heart in it, because it would have grossed her out. She thought it was really good. I probably couldn't have gotten away with this with my wife, who's super-sensitive to tastes, but as far as hiding offal in chili, this is about as good as it gets.
Side note, the dogs really liked the discarded water from cooking the heart. I added it to dry food and they gobbled it up with relish.