I love Chinese hot mustard on egg rolls but I was unable to find anything suitable in the several grocery stores we frequent. I looked up recipes on the Internet and found the one at the link below. When I looked at the ingredients (dry mustard, sugar, boiling water, and vegetable oil) I thought that can't work, but the reviewer's comments convinced me to give it a try. And it's perfect! The super spicy hotness obviously comes from the dry mustard, but all my life I thought mustard was more tangy than hot.
The other key point for the egg rolls shown below is that I baked them in our convection oven for 15 minutes which leaves the outside wrapper crispy and crunchy. Way better than the soggy microwave version.