How to Make It
Bring potatoes, water to cover, and 1 tsp. salt to a boil in a large Dutch oven over medium-high heat. Reduce heat to medium-low, and cook 10 to 15 minutes or until tender; drain. Cool 30 minutes.
Cook snow peas in 2 cups boiling water in a medium saucepan over medium-high heat 1 minute or until crisp-tender; drain, pressing between paper towels. Cut peas into 1/2-inch pieces. Cover with plastic wrap, and chill until ready to use.
Whisk together mustard, next 3 ingredients, and remaining 1/2 tsp. salt in a medium bowl; gradually add olive oil in a slow, steady stream, whisking until smooth.
Gently toss together potatoes and 1/2 cup dressing in a large bowl, and let stand 30 minutes. Just before serving, gently stir in peas, herbs, and remaining dressing. Add salt and pepper to taste.