Peel or scrub carrots; trim off ends. Cut into 3-1/2-inch/9 cm long batons.

Halve hot peppers lengthwise; with small spoon, scrape out seeds and discard.

Mix carrots and hot peppers with salt. Let sit, stirring a few times to evenly distribute salt, until carrots are tender, about 90 minutes. Rinse under cold water; drain well.

In dry skillet over medium-low heat, toast mustard seeds until they turn grey; transfer to mortar and crush coarsely (or wrap in wax paper and crush with bottom of heavy pan).

Separately toast coriander and cumin seeds until fragrant; mix well with mustard seeds, hot pepper powder, turmeric, and fenugreek (if using).

Divide equally, along with garlic, ginger and lemon rind, among 4 sterilized 500 mL canning jars. Pack jars with carrots and hot peppers, putting 6 hot pepper halves in each jar.

In saucepan, bring vinegar and sugar to boil; add lemon juice and return to boil. Pour into jars, leaving 1/2-inch/1 cm headspace. Seal with prepared discs and bands. Process jars, immersed in boiling water, for 10 minutes. When cool, shake jars to distribute spices. Let sit at least 10 days before opening. Refrigerate after opening.

Makes four 500 mL jars.