Cassia bark

Cassia is an aromatic bark, similar to cinnamon, but differing in strength and quality. Cassia bark is darker, thicker and coarser, and the corky outer bark is often left on. The outer surface is rough and grayish brown, the inside bark is smoother and reddish-brown. Cassia is less costly than cinnamon and is often sold ground as cinnamon. When buying as sticks, cinnamon rolls into a single quill while cassia is rolled from both sides toward the centre so that they end up resembling scrolls

One teaspoon ground = 1 stick. Substitute any ground cinnamon