Rose water is exactly as it sounds like - a flavored, scented liquid made by steeping rose petals in water. It’s been used as a flavoring in Middle Eastern, Indian and Chinese cuisines for centuries and is most often added to syrups and jellies (Turkish Delight anyone?) or sprinkled over cakes and creamy puddings like kheer (Indian rice pudding).
Confused by the directions to "wash your butter in rose water"? We were … until we tried making our own cultured butter. It's super simple and if you have a standing mixer to do the hard work, you won't even break a sweat (check out this link to find out how).
The final step in butter making is to rinse or "wash" the butter in cold water. This removes any remaining buttermilk (which spoils fairly easily) and increases the shelf-life of your butter. Could the direction in the knott biscuit recipe mean to rinse the butter in rose water? Seems a rather extravagant use of rose water. Why not simply add the rose water as you're creaming the butter?