Remove stems and seeds from dried chilies and cover in warm water. Place a weight (small bowl or cup) on chilies to keep submerged. Soak a minimum of 20 minutes. Drain chilies, reserving water. Coarsely chop chilies.

Place 6 clean 250 ml or 12 clean 125 ml mason jars on a rack in a boiling water canner. Cover jars with water and heat to a simmer (180°F/82°C). Set screw bands aside. Keep jars hot until ready to use. Preheating Bernardin® lids is not advised.

The sealing compound used for our home canning lids performs better at room temperature than it does pre-heated in simmering water (180°F). Simply wash lids in hot, soapy water, dry, and set aside until needed.

Preheating can lead to less vacuum being achieved during water bath canning, and to buckle failures during pressure canning. Prepare and measure tomatoes, onions and red bell pepper; set aside.

In a large stainless steel saucepan combine tomatoes, onions, red bell pepper, sugar, vinegar, cumin and coriander. Bring to a boil; reduce heat and simmer 40 minutes, stirring often. In blender or small food processor, combine chopped dried chilies, garlic, salt and 3 tbsp chili soaking water.

Process until a smooth paste is formed. Add paste to tomato mixture; simmer another 5 minutes, stirring often. Remove from heat. Ladle harissa into a hot jar to within 1/2 inch 1 cm) of top of jar (headspace).

Using nonmetallic utensil, remove air bubbles and adjust headspace, if required, by adding more sauce. Wipe jar rim removing any food residue. Centre hot sealing disc on clean jar rim. Screw band down until resistance is met, then increase to fingertip tight. Return filled jar to rack in canner.

Repeat for remaining sauce. When canner is filled, ensure that all jars are covered by at least one inch (2.5 cm) of water. Cover canner and bring water to full rolling boil before starting to count processing time.

At altitudes up to 1000 ft (305 m), process -boil filled jars - 10 minutes.* When processing time is complete, remove canner lid, wait 5 minutes, then remove jars without tilting and place them upright on a protected work surface. Cool upright, undisturbed 24 hours; DO NOT RETIGHTEN screw bands.

After cooling check jar seals. Sealed discs curve downward and do not move when pressed. Remove screw bands; wipe and dry bands and jars. Store screw bands separately or replace loosely on jars, as desired. Label and store jars in a cool, dark place.

For best quality, use home canned foods within one year.

Processing: At altitudes up to 1000 ft (305 m), process -boil filled jars - 10 minutes - 10 minutes.

Altitude-adjusted processing table: At altitudes up to 1000 ft (305 m), process -boil filled jars - 10 minutes