Bb Minor Major 9th, 2nd inversion (E# in the bass)
Also written as Bbm(maj9)/E#.
Notes, from the bass up
E# (bass)AB#A#C#
The same notes as Bb Minor Major 9th (E#, A, B#, A# and C#), rearranged so E# is the lowest note. Use it to move between chords with smaller jumps across the keyboard.