The ornamental design for a singlebladewhisk, as shown and described.
FIG. 1 is a perspective view of a single blade whisk showing my new design,
the handle shown in broken lines for illustrative purposes only and
forming no part of the claimed design;
FIG. 2 is a left side elevation view thereof, the opposite side being
identical;
FIG. 3 is a front elevation view thereof, the opposite side being
identical;