Preheat oven to 350°F. Grease 8-inch square baking pan and line with enough parchment paper to overhang edges; set aside. Whisk together flour, cocoa powder, cornstarch, salt and baking powder; set aside.
Melt chopped chocolate and coconut oil in heatproof bowl set over barely simmering water, stirring occasionally. Remove from heat. Stir in coconut sugar, maple syrup and molasses. Let cool slightly.
Stir in eggs, one at a time. Stir in beets, All Out Stout and vanilla. Fold in flour mixture until combined. Scrape batter into prepared pan; smooth top.
Bake for 25 to 35 minutes or until only a few moist crumbs adhere to toothpick inserted into center.
Let cool completely in pan on rack. Cover and refrigerate until firm, at least 4 hours or up to overnight. Using parchment paper as handles, transfer to cutting board. Dust with cocoa powder. Cut into squares to serve.
Tip: Fold in 1/2 cup chopped walnuts if desired.