Place a 15 by 9 inch piece of parchment paper.
Set aside.
(If using an oven place parchment into a 9 by 5 inch loaf pan and preheat oven to 350 degrees F.
In a large bowl use your hands to combine beef, salsa, mushrooms, green onions, seasoning, salt, chiles, and egg.
Form into a 9- x 5-inch loaf.
Place loaf onto parchment paper.
Hold the edged and gently place into a 5-quart slow cooker.
Top with jalapeno slices if desired.
Cover tightly and cook on low for 5 hours and 30 minutes.
NOTE: If using an oven cook for 1 hour or until beef is cooked through.
Garnish with additional salsa, guacamole and cilantro leaves if desired.