Stir salt into hot water until fully dissolved. Set aside.
In a bowl, beat marshmallow cream, shortening, powdered sugar, and vanilla on high until smooth and fluffy.
Mix in the salt water until fully incorporated.
Fill cupcakes or cake:
For cupcakes: Use a piping bag fitted with a round tip to inject filling into the center of each cooled cupcake.
For cake: Spread filling between the two cooled cake layers. Alternatively, you can use a 9x13 pan and pipe holes of it all over the cake.
Chocolate Ganache Topping:
Warm almond milk in a saucepan or microwave until just simmering — not boiling.
Pour hot almond milk over the chocolate chips in a heatproof bowl. Let sit for 1–2 minutes, then stir until smooth and glossy. Stir in vanilla.
Top cupcakes or cake:
For cupcakes: Dip tops into the ganache or spoon/pour it over.
For cake: Pour ganache over the top layer, allowing it to drip down the sides if desired and spread if necessary.
Allow ganache to set slightly on cupcakes before serving, or refrigerate briefly for a firmer top.
Decorate the tops how you desire with Vanilla Frosting *See Recipe