I love Boulevardiers and variants, and I agree with T. Magnatum (I'm getting older too) that this needs more than 4 pitiful drops of chocolate bitters to differentiate it from a standard Boulevardier. And the choice of chocolate bitters is up to you: I used 2 *dashes* of Bittermen's Xocolatl Mole bitters and 1 dash of Angostura Cocoa bitters and think they move the BV in a different, and tasty, direction. Serve it up so you can taste and smell its evolution as it warms in the glass.