In a clean, sanitized pint jar, pack the peppers in just enough water to cover. Add the salt and whey, shake the jar, and cover with an airlock or a regular lid-and-band. Place the jar in a warm place in your kitchen, away from direct sunlight and drafts.
Let the jar sit on your counter for about 3 to 4 days, shaking it and burping the lid regularly. Once the brine has become really cloudy, it should be ready for the next step.
Strain the brine out of the peppers into a bowl and save it. Use an immersion blender or a food processor to pulse the remaining soggy peppers. Add a little brine to loosen them up if needed. They should be pretty pureed when you are finished.
Pour half of the reserved brine, the pepper puree, and about 1/2 cup of apple cider vinegar back into the jar. Put a lid on the jar and shake it up well.
Place an airlock lid on the jar and let it get a bit bubbly by sitting the jar on the counter for 12 to 24 hours before placing a normal lid on the jar and putting the hot sauce into the fridge.
This sauce will slowly continue to get a sharper fermented taste if kept in the fridge. Stays good for as long as you enjoy the taste.