What is this shrub? (Southern California)
 

My two-year old, two-foot tall shrub is a broadleaf (not deciduous).

All of the stems are light green and have a bumpy surface (similar to
scales on a fish or shingles on a roof).

The petioles have an alternate arrangement and are spaced about every
1/2 inch along the stem.

The leaves are compound (multiple leaves arise from each petiole).
They have a linear shape (the midpoint is wider than its base and its
apex), have pinnate venation and have smooth margins. They are light
green color with a dull surface and they feel somewhat leathery.

The white star-shaped (?) flowers are single flowers (they do not grow
in spikes (racemes).

The shrub has a peppery taste even when one is just working the soil
near it or pruning it.

What is it?