Boil 250 grams of potatoes (cut into 2 cm cubes) in a large pot of salted water for 10-12 minutes, or until they are tender but still firm. Drain and set aside to cool.
In a separate pot, boil 150 grams of fresh or frozen peas for 3-4 minutes, or until they are tender. Drain and set aside to cool.
In a small bowl, whisk together 2 tablespoons of olive oil, 1 tablespoon of lemon juice, 1 teaspoon of mustard, 1/2 teaspoon of salt, and 1/4 teaspoon of black pepper to make the dressing.
In a large mixing bowl, combine the cooled potatoes, peas, 1/4 cup of finely chopped red onion, and 1/4 cup of chopped fresh coriander leaves.
Pour the dressing over the salad and gently toss to coat all the ingredients evenly.
Refrigerate the salad for at least 30 minutes to allow the flavors to meld together. Serve chilled.