Wash and thoroughly dry the kale. For small, tender leaves, just rough chop it a bit, while for tougher leaves remove the woody stems and cut into thin ribbons.
In a small bowl, whisk lemon juice into olive oil. Add 1/4 teaspoon of sea salt, the prepared horseradish, and all but the reserved strip of lemon zest. Whisk until the dressing is nicely emulsified.
Pour about half the dressing onto the kale leaves, and massage into the leaves with your finger tips. Wait a minute or two, taste, and add dressing or salt as needed.
Before serving, slice reserved zest into thin slivers. Add zest and Parmesan shavings (I use a vegetable peeler for mine) to the salad and toss.
This salad keep surprisingly well in the fridge for a few days and makes an excellent addition to your brown bag lunch.