http://www.seriouseats.com/2016/04/c...os-how-to.html

How to Master Flavorful Chiles Rellenos
J. KENJI LÓPEZ-ALT

I'm pretty sure that the only reason we used canned chilies back then is
that it wasn't possible to get good fresh Poblano peppers in New York in
the early '80s. That's not a problem anymore (and certainly not an issue
near my current home in the Bay Area), and both my recipe and my
technique have improved since those early can-based days. I've
experimented with various chili-roasting methods and dozens of batter
recipes and techniques, and I've finally nailed that salsa. Here's what
I've learned.

I sauté an onion in a little vegetable oil, add a big pinch of Mexican
oregano, then add the pork, breaking it up with a wooden spoon and
cooking it until it's heated through before adding it to my bowl of
grated cheese. The hot pork helps the cheese melt just a bit, which
makes the filling denser, stickier, and easier to place inside the
chilies without falling apart.