Crispula
H. 'Crispula'
Wavy dark green leaves with white margins, pinwheel-shaped clump.
RHS Plant Finder lists this as a species. This is disputed due to the plant exhibits distinctive H. montana characteristics.

Alternative: H. 'Mountain Snow'
Plant Size
  Large: 20" x 36"  
Leaf
  12" x 6"; dark green, white margins  
Flower
  Pale lavender  
Parentage
  H. montana background  
CrispulaCrispula