Spicy Hot Sauce – Turning Harissa into a Flavorful Hot Sauce

There are a few things that might work. I would probably just add more seeds. The majority of the capsaicin where the heat comes from is in the seeds, while the majority of the flavor is in the flesh. You could just add some seeds from a hot pepper like habanero or cayenne or even more jalapeno seeds.

You could also add some chili pepper that has heat but not a lot of flavor. Some examples include cayenne and chile de arbol. Thai bird and african bird chiles are hot and also don't have a ton of flavor in my opinion.

Another option is to try a chili extract. For example, a habenero extract will have some flavor, but a small amount will add an enormous amount of heat. So you may be able to get away with an amount small enough not to add much flavor, while at the same time kicking up your heat to the desired level.

Personally I like habenero, esp in El Yucateco sauce, which I often add straight to hot sauces.

Tasting the peppers is absolutely the only way, short of a chromatography machine. This is especially true for jalapeños from grocery. This because, as stated on this site here and in other answers by myself and others, pepper spiciness can vary greatly even on the same plant. Accordingly, chiles mixed possibly from plants, even from different harvests or suppliers, cannot be expected to have any reliable consistency of spiciness.

My approach is to pre-dice and freeze in batches. I use baggies, but another approach mentioned on this site here.

NOTE: The applicable advantage to this approach is that if you cook using the chiles often enough to warrant this approach, the heat level will be more consistent batch-to-batch.

My preservation process goes something like this:

• Purchase many fresh chiles at once depending on what you will use in 3-6 months. (I use 25 to 50)
• Sample the heat of each pepper during the preservation process
• Dice the peppers (de-seed beforehand if desired)
• Segregate into three groups:
  • Mild / non-spicy
  • Killer-blazing hot
  • Normal (everything in-between)
• Freeze into single-use sized baggies (~1¢ each, non-zip)
  • Place the smaller baggies into a larger gallon-sized zip-type freezer bag (~15¢ each) labeled with the spice level of pepper type, date processed, and heat level the contents.

Though I always keep seeds because I want the spice, this approach can be used with or without a de-seeding stage in the process. Another perhaps applicable note is that IME, without seeds, jalapeños spiciness falls within a narrowed range.

To reiterate in summary, one advantage here beyond preservation and availability is that as you have the three piles of diced chiles, the spice heat level of each batch segment tends to be nicely consistent.