Marinades using leftover liquid coffee sound like a great idea too. I’ve heard of making redeye gravy with leftover coffee, but I never think to save the leftover coffee from the pot to do so.
Here’s a recipe I found that looks like it might make a similar marinade. The main ingredients are brewed black coffee (I would use cold-brew coffee for a stronger but more mellow flavour), Worcestershire sauce, balsamic vinegar, Dijon mustard, and black pepper. I might consider adding red wine in addition to, or instead of, the balsamic.
I don’t like coffee at all but I don’t mind adding a bit of it to a chocolate cake recipe to make it like, deep-voice chocolate.
When I was staying at my mom’s while she was recuperating from a surgery, she always had coffee left over so I made a random chocolate-cake-with-coffee recipe and it was great! Especially with a lighter whipped frosting.
I used Trader Joe’s Coffee rub and found it pleasing, and it was in stores last time I checked, but it’s apparently seasonal. Here’s a copycat recipe.
1/4 cup ground coffee (medium to coarsely ground)
2 Tbsp. brown sugar
2 Tbsp. garlic powder
2 Tbsp. onion powder
2 tsp. cayenne pepper (can be adjusted to your spice preference)
2 Tbsp. paprika
1 Tbsp. ground cumin
1 Tbsp. salt
Of course, I’d turn UP most of those flavors, and sub smoked paprika or a sharp, but that’s me.
I find this works better with (duh) higher quality coffee. I have also found that marinating beef in a strong and/or smoked tea is an amazing option as well.