2. Slice the pepper in half lengthwise and remove the seeds. Place the 2 halves, skin side up, on a cookie sheet and press down so they lie flat.
3. Place the pepper under the broiler until the skin is evenly blistered, about 5 to 8 minutes.
4. Carefully remove the pepper from the cookie sheet and place in a bowl. Cover tightly with plastic wrap and let sit for 5 minutes. Uncover, peel off the skin and discard.
5. Puree the roasted red pepper and salt in a food processor.
6. Add the mustard and puree. Add the verjus and vinegar by the tablespoon, pureeing after each addition.
7. With the motor running, add the olive oil and stock slowly through the feed tube.
8. Stir in the chives and pepper. Adjust the salt and pepper to taste.