This will make enough for two, you could just double it for leftovers. You will need:
1 pack of veal or lamb. You can buy it ground, or just get whatever cheapest and grind it yourself. If you grind it yourself, if you buy it unfrozen, put it in the freezer for about 20 minutes and then throw it in a food processor. If you buy it frozen, let it thaw until you can poke it with a finger but it's still frozen inside, then throw it in a food processor and grind it.
One red onion (a white one would work too)
Two portobello mushrooms
Some bread crumbs, if you have them (like enough to cover your palm)
Some sage, some garlic, some black pepper, some salt, some basil, and some oregano
First, pop the stems off of the mushrooms and hang onto them. Preheat the oven to 400 degrees. Using a razor or a sharp knife, make little crosshatches on the portobellos. Drizzle a little olive oil on the baking sheet, put the mushrooms cap side down, and put them in the oven. They'll hang out in the oven while you're cooking the rest of the stuff.
Put a large saucepan on the stove on medium heat. Dice the onions and throw them in the saucepan. Cook them for a few minutes, then put in the ground veal or lamb. Throw a sprinkle of salt, a sprinkle of pepper, a sprinkle of sage, garlic, basil, and oregano, and pop the cover on the saucepan. Chop up the portobello stems and put those in too. Let that hang out what the meat cooks.
Check out the mushrooms. You'll see that some water is coming out of them, so turn them over so their caps are facing up and let them keep cooking (the idea is to get them to dry out a little bit).
Let the meat cook until it's browned and the onions are soft. It won't take long, maybe 15 minutes. Turn the heat off.
Take the mushrooms out of the oven and let them cool enough so that you can touch them without burning yourself. When they're cool, chop them into little squares and throw them into the meat mixture. Stir them up and add the breadcrumbs if you're using them.
Since the oven will still be warm, put the tortillas in there to heat up, and then put them on a plate and put the meat into the tortilla.
It'll be really good. If you want asparagus like I had, I just bent the asparagus until they snapped, threw away the woody ends, cut the asparagus in half, and cooked them on medium heat in a pan with bacon grease until they had browned spots and were softened. If you don't eat pork, use butter instead. You could throw some garlic in too (fresh chopped up, dried, or minced in a jar) if you like garlic as much as I do.
And that's it!