Chipotle peppers are red jalapeno peppers that have been smoked. Their characteristic spicy, smoky flavor makes them staples in Spanish, Mexican and Tex-Mex cuisines. Chipotles are sold in many forms, including dried, powdered, pickled and canned, but they're not always readily available. Here are some potential substitutes with relatively similar heat and flavor.
Any hot pepper can be used to achieve the heat of the chipotle, including fresh jalapenos, serranos or poblanos. The amount of heat imparted by the peppers can be altered to suit individual tastes: For a milder flavor, remove the inner membrane and seeds; for more heat, leave the seeds and membrane intact. Dried cayenne pepper or hot sauce would also work.
Chipotles are smoked, and though replacing them with another hot pepper adds heat to a dish, the distinct smoky flavor will be missing. A good substitute is another type of smoked hot pepper like pasilla de Oaxaca. Many supermarkets carry a variety of canned, jarred or dried smoked peppers.
Chipotles in Adobo
Chipotles are often sold canned in adobo, an herb- and tomato-based sauce. A good substitute for this type of chipotle is any of the aforementioned peppers mixed with a steak sauce. This replicates the flavor and consistency pretty well in a pinch.