Remove the seeds and stems from the Hungarian peppers. Place in a food processor and process until they are chopped to the size you like. I like mine eensy weensy, so I just pulverized mine. Set aside.
In a large stockpot, add in the flour and sugar. Whisk until combined.
Add in about half of the mustard and whisk until everything is completely incorporated and there are no lumps from the flour.
Add in the remaining mustard, peppers, vinegar, water, and salt. Mix with a spatula and everything is combined. Place over medium heat and stir occasionally.
Once the hot pepper butter comes up to a boil, stir constantly as it will burn easily. Let it cook to your desired thickness. I cook mine about 20 -25 minutes until it becomes quite thick.
Place your pint jars and lids into the canner to sterilize them.
Remove one jar at a time and ladle in your hot pepper butter. Wipe the rim clean and pull a lid out of the canner. Tighten the lid on with a band.
Once all the jars are filled, water bath for 10 minutes.
Remove from canner and place hot towel over top of the jars.
This recipe was adapted from CrazyCyndi via Food.com