Place the sliced cucumbers in a large bowl. Slice the white onion thinly and add it to the same bowl with the cucumbers.

Sprinkle the kosher salt evenly over the cucumbers and onions. Let the mixture sit at room temperature for about 2 hours, or until the cucumbers release enough liquid to almost cover them.

Drain the cucumbers and onion thoroughly, then rinse with cold water to remove excess salt. Taste a cucumber slice to check the saltiness; rinse again if needed.

Add the white vinegar, heavy whipping cream or sour cream, and chopped fresh dill to the bowl with the drained cucumbers and onions. Stir everything together until well combined.

Serve immediately or cover and refrigerate until ready to serve.