Wikipedia says:
The bean pods of the mesquite can be dried and ground into flour, adding a sweet, nutty taste to breads, or used to make jelly or wine.
When used in baking, the mesquite bean flour is used in combination with other flours – substitute ¼ cup-to-½ cup mesquite flour for each cup grain flour. Mesquite bean flour is used in breads, pancakes, muffins, cakes and even cookies. Mesquite powder is also high in calcium, magnesium, potassium, iron and zinc, and is rich in the amino acid lysine.
It is also reminiscent of Chai, as it has a spicy, almost cinnamon-ish (is that a word?) flavour. Makes a delicious drink when mixed with hot milk.
I have been adding it to brownies (replacing 2-3 T of flour for the mesquite), and will soon be trying a mesquite-buckwheat crepe! Pictures and recipe to follow.