Make hot fudge sauce: In a small saucepan over medium heat, combine heavy cream, milk, granulated sugar, butter, cocoa powder, vanilla, and salt. Whisk constantly until mixture thickens and bubbles gently, about 5 minutes. Remove from heat. It will thicken more as it cools.

Make caramel sauce: In a separate saucepan over medium heat, whisk together brown sugar, corn syrup, water, and baking soda. Bring to a boil, then reduce heat to low. Simmer without stirring for 4 minutes until deep amber. Remove from heat, carefully stir in vanilla (it will bubble up). Let cool slightly.

Toast nuts: Spread chopped nuts on a baking sheet in a single layer. Bake at 350°F for 5-7 minutes until fragrant and lightly browned. Let cool.

Set up station: Arrange ice cream in a large bowl or individual scoops in a chilled dish. Place hot fudge and caramel in separate small bowls. Arrange all toppings in individual glass bowls with small spoons.

Serve: Let guests scoop their own ice cream, then drizzle sauces and add toppings as desired.