How to Make It
In a large heavy skillet, melt 2 tablespoons of the butter in the oil over high heat. Add the carrots and toss to coat evenly. Cook, stirring frequently, until they begin to char and blacken around the edges, 20 to 25 minutes.
Transfer the carrots to a food processor and add the milk, lemon juice, salt, pepper and remaining 4 tablespoons butter. Puree until smooth.