Step 1

Chop the cucumbers in half longwise, then into thin half-moons. Layer in a medium-sized bowl, sprinkling each layer lightly with salt. Put two small plates on top then cover the bowl with plastic wrap. Refrigerate for at least an hour, or overnight.

Step 2

Put the cucumbers into a large colander and drain any excess water. Pat lightly with a kitchen towel to remove as much moisture as you can.

Step 3

Heat a small skillet over medium-high heat. Add the mustard seeds and cook, shaking the pan, until the mustard seeds pop just a bit. This should take no more than a minute or two. Take the skillet off the heat and pour the seeds into a plate to cool.

Step 4

Toss the cucumber slices with the shallots, sour cream, and chopped dill. Mix in the cooled mustard seeds. Taste and season with black pepper. You can serve this immediately, or refrigerate it for up to a day before serving.