How to Make It
Peel the carrots and then cut the carrots into rough 1-inch (2.5 cm) cubes. These do not have to be perfect, as they will all eventually be puréed.
In a bowl, toss the carrots with 2 tablespoons of the grapeseed oil and the salt and set aside for about 10 minutes. Transfer the carrots to a food processor and blend until broken up.
Transfer the mixture to a saucepot or large sauté plan. Set the pan over medium-low heat, cover, and cook, undisturbed for 40 to 45 minutes. You’ll know it’s ready when you can smear it with a spoon. (If you take it off the heat too early, you will find the texture of the purée to be somewhat grainy after you purée it.) Transfer the mixture to a blender and blend on low speed, then gradually increase to high speed while slowly frizzling in the remaining 4 tablespoons grapeseed oil. Blend the purée to the consistency of mayonnaise. Season to taste with salt; it should have a pure carrot flavor. Store in an airtight container refrigerated for up to 3 days.