Preheat oven to 350 degrees F. Lightly grease a mini muffin tin with cooking spray. Set aside

In a large bowl, cream together the butter and both sugars until light and fluffy, about 3 minutes. Add the egg and vanilla extract and stir until well combined. Stir in the flour, baking soda and salt until just incorporated. Scoop out about a tablespoon of dough into each mini muffin. Create a "cup" by flattening the dough down and bringing it up the sides. Bake until golden brown and almost set in the center, about 10 to 12 minutes. Remove from oven and let cool completely. If the cookies puff up too much, use a teaspoon measuring spoon to scoop out the center of the cool cookie.

Meanwhile, to make the hot fudge sauce, in a medium saucepan, heat the cream over medium heat until it is hot (but not boiling). Add the chocolate, sugar, butter and salt and stir until they are fully dissolved. Continue to cook, on low, until smooth and heated through. Remove from heat and stir in the vanilla extract. Allow to cool before topping. You can refrigerate it for up to 2 weeks, in an airtight container.

To assemble the sundaes, place a banana slice in each of the cooled cookie cups. Top with a small scoop of ice cream. Freeze for at least 1 hour to set or overnight. Right before serving, top with hot fudge sauce, chopped nuts, whipped cream, cherries, or jam as desired. Serve and enjoy immediately.