What if I want to add jalapenos to this casserole?

I had this casserole at a Food52 event and it was indeed delicious. Jalapenos sound like a great addition and I like the idea of fresh TBH, as well as Nancy's idea of serving as a garnish.

I would use whatever you have on hand or prefer, fresh or pickled.

Maybe the first time serve them as a garnish, so people at table can decide how much (or, if any) heat they want to add...according to their tolerance or preference for jalapeno.

If you all like them and you know the heat tolerance, yes - as suggested - add in Step 5.

(From someone who made an IsoGrits map of the USA - the line divides on where, in a diner, you are automatically served hash browns or grits with your breakfast.)

Jalapeños sound amazing for this! I'd use pickled. Dice them, and add at step five.