Place the potatoes in a saucepan and cover with water. Season the water with salt. Bring the liquid to a boil and reduce to a simmer. Cook the potatoes for 10 to 12 minutes or until fork tender. In a small saute pan, over medium heat, render the andouille until crispy, about 4 to 6 minutes. Drain the potatoes. Place the potatoes back in the pan and add the andouille, 1 tablespoon butter and 1/4 cup cream. Using a hand-held masher, mash the potatoes until smooth. Season the potatoes with salt and pepper. Set aside and keep warm. Drain the oysters, reserving the liquor. Set aside. In a large saute pan, over medium heat, add the oil. When the oil is hot, add the onions. Season with salt and pepper. Saute for 2 to 3 minutes. Add the garlic and parsley. Cook for about 2 minutes. Add reserved oyster liquor, Worcestershire sauce, hot sauce, and lemon juice. Bring the liquid to a boil and reduce to a simmer. Cook for 4 to 5 minutes or until the liquid thickens. In the sauce pan, stir in the remaining butter and cream. Season with salt and pepper. Season the oysters with salt and pepper. Add the oysters. Simmer for about 2 minutes or until the edges curl. To serve, mound the potatoes in the center of each bowl. Spoon the oysters and sauce around the potatoes. Garnish with the croutons.