Preheat oven to 325 F. Prepare two baking sheets by lining with parchment or silicone mats.
In a stand mixer or bowl, cream the vegan margarine with the sugar. Beat in the rice milk and vanilla. In a medium bowl, whisk the flour, cocoa, and salt. Mix into the wet mixture, it will make a stiff dough.
Scoop two tablespoon-sized portions and form into disks, then use a metal spatula to flatten. Dip the spatula in flour to keep it from sticking. Flatten each cookie to 1/4 inch thick.
Bake for 8 minutes, turn pans, then bake for about 8 minutes, check at five for scorching. The cookies will have a golden brown edge. Cool on racks.
Freeze the cookies before filling. Use a spoon to scoop slightly softened ice cream on a cookie, smooth the edges, and place another cookie on top, freeze.
Keeps tightly covered for up to a month.