Place the quartered potatoes in a large pot filled with salted water and bring to a boil. Cook the potatoes until they are tender and can be easily pierced with a knife, which will take about 20 to 25 minutes. Once cooked, drain the potatoes and put them back in the pot.
Mix in the mayonnaise, dry mustard powder, yellow mustard, celery, shallots, salt, and a good amount of black pepper. Use a potato masher to smash the mixture until you reach your desired consistency, keeping some chunks of potato if you prefer.
Cool the potato salad in the refrigerator until it is chilled. Before serving, taste and adjust the seasonings to your liking, as flavors will develop and mellow while chilling.
Notes
Serves 4 to 6. This recipe was first published in April 2012.