1 large Idaho potato, 3/4 to 1 pound, peeled and diced
1 tablespoon butter
3/4 cup plus 2 tablespoons heavy cream
Freshly ground white pepper
2 dozen shucked oysters, with their liquor reserved separately
2 slices bacon, chopped
1 tablespoon minced shallot
1/2 teaspoon minced garlic
1/2 cup thinly sliced fresh spinach leaves
4 crisp-toasted 1/2-inch slices of French bread, for serving
Place the potatoes in a saucepan and cover with water. Season the water with salt, bring to a boil and reduce to a simmer. Cook the potatoes for 10 to 12 minutes or until fork tender. Drain potatoes in a colander then put through a potato ricer until smooth and return potatoes to the pan (or, alternatively, mash the potatoes until smooth.) Add 2 tablespoons of the heavy cream, the butter, and salt and pepper and stir to combine. Cover, remove from the heat, and set aside to keep warm while you make the stew.
In a medium saucepan over medium heat, cook the bacon until crisp and the fat is rendered, 4 to 6 minutes. Using a slotted spoon, transfer the bacon to paper towels to drain and set aside. Remove most of the bacon drippings from the pan and discard or save for another purpose.
To the remaining drippings in the pan, add the shallots and garlic and cook until soft and fragrant, 2 to 3 minutes. Do not allow to brown. Add the remaining heavy cream and any reserved oyster liquor. Bring to a boil, reduce heat to a simmer, and cook until thickened slightly, 4 to 5 minutes. Add the spinach and season with salt and pepper to taste.
Add the oysters to the hot cream mixture and simmer just until the edges begin to curl, about 2 minutes.
To serve, mound the potatoes in the center of each of 4 shallow soup bowls. Spoon the oysters and sauce around the potatoes. Crumble the reserved bacon and sprinkle over the oysters. Garnish with the croutons and serve immediately.