Harissa is a hot chile paste found across the Maghreb but considered a cultural icon of Tunisia (the biggest exporter of harissa). It's become an integral part of Moroccan cuisine.
This recipe comes from about.com's Moroccan food section. It yields about 3 tablespoons but can be scaled upwards as needed.
Ingredients:
12-15 dried red chiles (1.5 oz or 100 grams)
3-4 cloves garlic, peeled
1 tsp salt (or to taste)
1 tsp cumin, ground
1/2 tsp coriander seeds, ground
1/2 tsp caraway seeds, ground
2-3 tsp lemon juice
olive oil
Procedure
[1] Remove the seeds and stems from the chiles. Place them in a heatproof bowl and pour over enough boiling water to cover. Let soften 30 minutes to an hour.
[2] Grind the dried spices to a powder (a coffee grinder works well for this) if you are starting with whole seeds. Traditionally one dry-fries the whole seeds over moderate heat until the aroma comes up (about a minute), but that step is optional. You can start with pre-ground cumin, coriander, and caraway if you wish.
[3] Drain the chiles and gently press out excess water with a paper towel. Grind the chiles, garlic, salt, cumin, coriander, and caraway to a paste. Traditionally this is done with a mortar and pestle, but a blender or mini food processor works, too. Add the lemon juice and just enough olive oil to moisten the harissa (use more olive oil if it seems dry).
Unused harissa can be stored in the refrigerator in an airtight container. For long-term storage, lightly top the harissa with a small amount of oil before covering. It will keep refrigerated for months. I have not tried freezing it, but I imagine that will work, too.
Notes:
The online recipes I've seen suggest using chiles de arbol. The Bon Appetit recipe throws in 2 guajillos and an ancho as well. Your choice and number of chiles controls the heat level. I've never tried them, but I would imagine that using dried red bird's eye chiles (aka Thai chiles) would give you a very hot harissa, indeed.
Some harissa recipes add a bit of tomato paste. For rose harissa, add rose water and/or rose petals.
The procedure for making harissa is identical to the way that most Thai curry pastes are made. The only difference is the ingredients.
The old school method for grinding is a mortar and pestle. You start with the driest ingredients (the toasted whole spice seeds and salt). When they are ground fine, you add the remaining ingredients in order of increasing moisture: First the chiles, then the garlic, and finally the lemon juice (and olive oil, if using).
I usually make several times this recipe at once, since it keeps so well under refrigeration.
-Paul W.