Place 4 ounces dried chilies (stemmed and seeded) in a large heatproof bowl and pour in enough boiling water to fully cover them. If needed, weigh the chilies down with a plate so they stay submerged. Soak 10–15 minutes, until completely softened. Drain in a colander and press or pat the chilies to remove excess water.

While the chilies soak, heat a small skillet over medium-low. Add 1/2 teaspoon caraway seeds, 1/2 teaspoon coriander seeds, and 1/2 teaspoon cumin seeds. Toast, stirring or shaking the pan frequently, until the seeds are fragrant and lightly darkened, about 5 minutes. Watch closely to avoid burning. Remove from heat and let cool briefly.

Transfer the cooled toasted spices to a small spice grinder or a mortar and pestle and grind until very fine.

Put the drained chilies, the ground spices, 4 peeled garlic cloves, and 1 teaspoon salt into a food processor. Pulse and then process until the mixture forms a thick paste, stopping to scrape down the bowl and blades as needed.

With the processor running, slowly drizzle in 3 tablespoons olive oil until the paste is smooth and cohesive.

Taste and add more salt if desired. Use the harissa paste immediately or store as you prefer.