In a small pot, combine the sugar, cocoa powder, and salt. Add the ½ cup non-dairy milk, and stir constantly over medium heat.
Bring the sauce to a simmer, then reduce the heat to low.
Add the peanut butter and vegan buttery spread stir until smooth and melted.
Put the cornstarch and the 2 Tablespoons non-dairy milk in a small container with a lid and shake well until combined. Slowly pour the cornstarch mixture into the pot and stir until the hot fudge thickens.
Remove the pot from the heat and set aside so the hot fudge cools enough to serve.