In a large bowl, toss shrimp with ¾ teaspoon all purpose seasoning, ¾ teaspoon dried cumin, and 1 teaspoon chili powder. Set aside.
Add ½ tablespoon of oil to a large skillet and heat until hot. Stir in the mushrooms, onions, red bell pepper, pickled jalapenos, and garlic cloves. Cook for 7 minutes, until the mushrooms have released their water and onions are translucent. Transfer the vegetable mixture to a small bowl and set aside.
Over medium high heat, add remaining ½ tablespoon oil and heat until hot. Add the shrimp mixture to skillet and cook for 5 minutes, until shrimp just turn opaque. Remove from the heat and set aside to cool.
For the jalapeno cream sauce
In a medium saucepan, melt the butter until bubbly. Whisk in the flour, salt, and pepper, and cook stirring constantly for 1 minute, until the flour mixture begins to brown lightly.
Whisk in the chicken broth, jalapenos, and jalapeno brine. Continuously whisk and cook over medium heat for 3 minutes, or until sauce begins to bubble and thicken.
Stir one cup of the Monterey jack cheese into the cream sauce. Cook and stir until cheese has melted. Remove from the heat and set aside
How to make the enchiladas
Fill each tortilla with shrimp filling by spreading ¼ cup shrimp mixture slightly to the edge of one side of the tortilla.
Roll to enclose the filling and lay the enchilada seam-side down in prepared baking dish that has been sprayed with cooking spray.
Pour the jalapeno cream sauce over top of the enchiladas and bake at for 30 minutes, or until sauce is bubbly.
Remove the enchiladas from the oven and sprinkle with cilantro leaves. (if using)