I believe QSis nailed it. I can't find a recipe either
It is talked about but I can't put my fingers on an actual recipe. It's always described as a basil, spinach cream sauce. I would start with making your own basil, spinach pesto and adding some cream to it.
You can start with this recipe and then when heating add small amounts of cream until you think it looks right.
2 cups (packed) fresh spinach leaves
2 cups (packed) fresh basil leaves
2 TBS chopped garlic
about 2/3 cup pine nuts
1 1/3 cup grated parmesan cheese (fresh, not the "green" can)
juice of 1 lime
2/3 cup extra virgin olive oil
Put everything except the oil in a food processor (not a blender) and pulse away. Once it starts breaking down slowly drizzle in oil until you reach a consistency you want. You may not need all of the oil either. Keep it thicker since you are mixing it with the cream.