Grind the mustard seeds in a spice mill or coffee grinder until they are the texture of coarse cornmeal. Transfer to medium-sized bowl. Add the powdered mustard, water, vinegar, and orange juice, and stir well. Let stand for 2 hours then stir again.

Add the apricots, coriander seeds, and salt & pepper then mix again.

Freshly made, this mustard has a powerful bite. The book says to let it sit in the refrigerator a few days to let it mellow. I say a few days AT LEAST! The book also says this will keep, covered and refrigerated, for 2 to 3 weeks. I had a big batch in my fridge for something like 6 months with no apparent ill effects.