Cook the new potatoes in salted boiling water for about 10 minutes or until tender, drain and cool.
Cook the bacon in a frying pan until crisp, remove from the pan and then cook the onion in the bacon juices until soft. Finely chop the bacon.
Take the potatoes and lightly crush with the back of a fork and transfer to a large mixing bowl along with the bacon and cooked onion. Make the dressing by mixing the oil, vinegar, dill and mustard together. Pour this over the potatoes and mix well.
Finally, fold in the chopped gherkins and hard-boiled egg and serve.
A hard-boiled egg will take 7-8 minutes.