How to Make It
Preheat the broiler and position a rack 8 inches from the heat.
Fill a medium bowl with ice water. In a medium saucepan of salted boiling water, blanch the spinach just until wilted, about 1 minute. Drain, then transfer to the ice bath to cool completely, about 3 minutes. Drain, squeeze dry and finely chop. Transfer the spinach to another medium bowl and add the shallots and pastis. Season with salt and pepper and mix well.
Arrange the oysters on a baking sheet. Spoon the spinach on top and dot with the sour cream. Broil for about 10 minutes, until golden. Serve warm.