Bring a large pot of salted water to a boil. Prepare an ice water bath by filling a bowl halfway with ice and water; set aside.

Add kale and spinach to the boiling water and cook until wilted, about 2 minutes. Remove from the boiling water and plunge into the ice bath. Once the greens are cool, remove them from the ice bath, shake off any excess water, and place in the bowl of a food processor.

Add garlic, pine nuts, and vinegar and, while puréeing, slowly pour in the olive oil. Continue puréeing, stopping to scrape down the sides of the bowl with a rubber spatula as necessary, until all of the oil is incorporated and the mixture is smooth, about 4 minutes. Season with salt and serve.