Fines herbes, a mixture of parsley, chervil, tarragon and chives, is a classic combo in French cooking. The herbs give this simple sauce, which is similar to hollandaise, a delightful lift.
Place mayonnaise in a small saucepan. Gradually add broth, whisking until smooth. Heat over medium-low heat, whisking constantly, until heated through but not bubbling, about 2 minutes. Remove from heat and stir in mustard, oil, lemon juice, parsley, tarragon, chives, chervil and pepper. Serve warm.
Tip: If you don't have fresh chervil, use more fresh parsley instead.