Step 1

Preheat oven to 400°F.

Step 2

Line a rimmed baking sheet with parchment paper and arrange chiles on it in a single layer. Roast chiles for 30 minutes then transfer to bowl and cover for at least 15 minutes or until cool enough to handle.

Step 3

When chiles are cool enough to handle, remove stems, skin and seeds; coarsely chop.

Step 4

Meanwhile, heat olive oil in a large saucepan over medium heat. Add tomatillos, onion, garlic and jalapeño; cook and stir until soft, about 15 minutes. Add chopped chiles, cumin and water and bring to boil. Reduce heat, cover and simmer 10 minutes, stirring occasionally. Season to taste with salt and pepper.

Step 5

Blend in 2 or 3 batches, taking care to have a similar ratio of liquid to solids and covering the blender with a towel not the lid if the sauce is hot.

Step 6

Pour sauce into canning jars or other heat-safe containers and let cool. Refrigerate or freeze sauce or use it right away!