Preheat the oven to 250 degrees F.
Combine the chocolate chips, 1/2 cup of the heavy cream, the condensed milk and salt in a medium saucepan over medium-low heat. Stir until the chocolate chips have completely melted and the sauce has thickened, 3 to 4 minutes. Turn off the heat and cover with a lid to keep warm. If the hot fudge needs to be heated up later, simply warm it over low heat, stirring constantly, until it is easy to drizzle. Add up to 1/4 cup of heavy cream if you want a thinner sauce.
Whisk the remaining heavy cream in a mixing bowl until soft peaks form. Cover with plastic wrap and refrigerate.
Cut each honey bun in half horizontally. Set a two-burner griddle or a large nonstick skillet over medium-low to medium heat. Add 3 tablespoons of the butter if using the griddle, or 2 tablespoons if using the skillet. When the butter has melted, cook the honey bun halves in batches, cut-side down until golden brown, 3 to 4 minutes. Remove to a baking sheet and place in the oven to stay warm. Add the remaining butter to the griddle or skillet and cook the remaining honey bun halves.
To assemble, place 2 honey bun halves onto each serving plate. Serve each honey bun with 1 to 2 scoops of ice cream, a generous drizzle of hot fudge sauce and a dollop of whipped cream. Serve any extra hot fudge sauce on the side.