Place the butter in a large pot over medium heat. Melt the butter and then add the onions. Cook the onions for 2 minutes, stirring occasionally. Add the potatoes, stock, and salt then bring to a simmer. Cook for about 10-15 minutes until potatoes are fork tender. Stir in the cream and cook until hot (but not boiling). Add the shrimp and cook until no longer pink, about 3-4 minutes. Stir in hot sauce, season to taste and serve.