Place the charring vegetables on a hot grill, rotating about every 4 minutes, until all sides are blistered.
Put them in a large bowl and cover with saran wrap.
Set aside to cool a bit.
Break off the stems and pour out the seeds of the toasting peppers.
Toast off the dried chilies and cumin seeds in a hot pan, for about 30 seconds, turning over once.
Remove from the heat and place in a bowl, pouring the 4 cups of boiling water over and set aside to steep. Letting steep for about half an hour.
Scrape the charred skin off and de-seed the charred vegetables.
Add all ingredients to a large blender (steeping liquid, peppers, charred vegetables, stock, seasonings.)
Whiz until a sauce is formed. Don't forget to be careful as there are hot vegetables and hot liquid involved!