Roast beef and horseradish sauce are as English as Big Ben. Fresh herbs add a Mediterranean touch.
Step 1: If using fresh horseradish, finely grate it or chop it in a food processor fitted with a metal blade. (If using the food processor, cut the horseradish into 1⁄4-inch-thick slices before processing.) Whichever method you use, take care not to breathe the potent horseradish fumes.
Step 2: Combine the grated horseradish, sour cream, herbs, lemon juice, lemon zest, salt, and pepper in a nonreactive bowl and whisk to mix.
Step 3: Place the cream in a large chilled bowl and beat it with an electric mixer until soft peaks form. Gently fold the whipped cream into the sour cream mixture. Taste for seasoning, adding salt, pepper, and lemon juice as necessary. Refrigerate, covered, until serving. The horseradish sauce tastes best served within a couple of hours of making, but it will keep for a few days in the refrigerator.