MAKES 1 CUP Active: 20 min. • Total: 50 min.
So called because it contains butter and ice, which keep the sauce stable and bright green even after baking, this “fake” pesto works with any green. Toss it with toppings like shaved zucchini or potatoes before baking the pie. 3 oz. assorted herbs or green vegetables (fava beans, peas, basil, sorrel, mint, green garlic, chervil, basil, nettles, etc.) ⅓ cup extra-virgin olive oil 2 Tbsp. cold unsalted butter, cubed 1 Tbsp. (¼ oz.) Parmigiano-reggiano 1 In a blender, add the greens, oil, butter, and cheese, and 1–2 ice cubes (about 1 ounce total). Blend until the sauce is emulsified and the consistency of Greek yogurt. (If the blender gets hot, let it rest; the sauce should remain cold.)
2 Transfer sauce to an airtight container in the coldest part of the fridge to set, at least 30 minutes or up to 72 hours.