Looks like a form of European Allium senescens ssp. montanum, green-leaved versus the Asian forms of A. senescens that are typically gray-leaved. The European "senescens" has reverted back to an earlier name, and is now known as Allium lusitanicum. The plant is not only very variable, it'll hybridize with just about any other rhizomatous Allium nearby, so senescens-like hybrids are very common in horticulture. The plant shown is a lovely one.
