Update on this one. I started out with a cured corned beef flat about 4.5 lbs and soaked it overnight to make sure it wasn't too salty. Rubbed with the pack that came with it along with some cracked pepper and a steak rub I had on hand. I cooked the pastrami on my kamado joe with plenty of wood chunks until it hit 155 then it went into the anova sous vide for 24 hours at 155. I was disappointed when it came out of the smoke. Flavor was good but it was not tender at all. 24 hours in the sous vide fixed that though and it was fantastic. Glad I asked the question because I would not have known to do that and it turned out great. That will be my preferred method from now on.
A brisket, fresh or corned won't be tender at 155°. Many people do a wrapped finish, or just slice it really thin, but a dedicated finish is generally better. I like a pressure finish as it takes 40 minutes plus some release time. Sous vide is also great, just takes longer than a steam or pressure finsh. SV and pressure finish give you some wonderful broth, save it for reheating juice, or making a pastrami 'dip' sandwich or a Reuben soup base.
The pack of spices in a corned beef are used when making corned beef. Pastrami spices are keyed to pepper, garlic, coriander etc. I do use some Montreal seasoning in my pastrami rub, so you might play around with other flavors. If you don't like the coriander flavor, I also added my Garlic Pepper Seasoning recipe, it's much lower in salt than store-bought garlic pepper, and you could eliminate the canning salt all together when using as a pastrami rub.
thirdeye's Pastrami Rub.
(
from the Playing With Fire and Smoke cookin' site. this recipe makes enough rub to season several corned briskets, any leftover can be stored in a zipper baggie in the freezer for several months)
4 tablespoons freshly ground black pepper (more if you like it peppery)
1 teaspoon ground coriander
1 teaspoon granulated garlic powder
1 teaspoon onion powder
2 teaspoons Canadian/Montreal Steak seasoning
1/2 teaspoon thyme, dried
1 teaspoon paprika
Combine all ingredients and mix thoroughly.
thirdeye's All-Purpose Garlic Pepper Seasoning
Ingredients:
3 teaspoons Garlic Powder
3 teaspoons Black Pepper
1 teaspoon Canning Salt (consider omitting for pastrami)
1/2 teaspoon Toasted Onion Powder
1/4 teaspoon Paprika