There is no easy answer or solution to this age-old problem. If you have overcooked potatoes, there are one of two things you can do: go ahead with the recipe as planned but will come out clumpy. Or what I would suggest is mash the potatoes slightly and add the dressing and serve as smashed potato salad. It tastes exactly the same, just a softer texture. Make sure it isn’t as mushy as mashed potatoes. But if you chronically overcook potatoes, steam them for this salad. Sometimes it takes a bit longer to get them as tender, but it is well worth the effort.