Preheat the oven to 350 degrees F and line a baking sheet with parchment paper.  

If needed, in a small bowl, combine the egg replacer with water as directed on the package.  Let sit for 2-5 minutes before adding to the recipe.  

In a medium sized bowl combine the flour, salt, and baking soda and whisk to combine.  Set aside. 

In a large bowl, combine the softened butter and sugars and whisk until fluffy.  Add the egg (or egg replacer) and mix until combined.  

Add the dry ingredients to the wet and mix until combined.  Fold in the vegan chocolate chips, marshmallows, and pretzel pieces.  

Form dough into 1-2" balls and place about 2" apart on the baking sheet.  Bake for 10 minutes, until edges are golden brown.  Pro tip: try to make sure the marshmallows end up in the center/on top of the cookies not the sides. 

Remove cookies from oven and let cool for about 5 minutes until transferring to a wire rack to cool completely.  Repeat for remaining dough.  

Store leftover cookies in an airtight container for up to 4 days.