For the cupcakes: Preheat oven to 350F. Line a 12-hole cupcake pan with paper liners (this recipe makes 11 cupcakes, so you can leave a hole empty!). Set aside.
In a medium bowl, sift in flour, sugar, salt, baking soda and cocoa powder. Whisk to combine.
Using a spoon, make 3 wells in the dry ingredients, one large well and two smaller wells. Pour the grapeseed oil into the largest well, the vinegar into one of the smaller wells, and the vanilla extract into the last well. Pour the cold water over everything and whisk the ingredients together until the mixture is smooth.
Fill cupcake liners ¾ full with batter. Bake for 15-20 minutes. They are done when the tops spring back when lightly pressed in the center (or you can do the toothpick test).
Remove from the oven and cool in cupcake pan for a few minutes, then transfer to a wire rack to cool completely.
For the frosting: In the heatproof bowl of an electric mixer, set over a saucepan of simmering water, combine sugar, corn syrup, ¼ cup water, and egg whites. Cook over medium heat, whisking frequently, until mixture registers 160 degrees on a candy thermometer.
Attach the bowl to a stand mixer fitted with the whisk attachment. Beat mixture on high speed until glossy and voluminous, 3-4 minutes (do not overbeat). Beat in vanilla. Pipe onto cooled cupcakes as desired (I used a large round tip).
Process Oreos in a food processor until they are ground into fine crumbs. Sprinkle the crumbs over the frosting and decorate with your Halloween decor.