How much black garlic to substitute for regular garlic in a slow-cooker? My wife and I are currently making a slow-cooker brisket taco recipe and decided to substitute black garlic for the garlic it called for. The recipe called for two medium cloves and I used the same amount of black garlic.

However, after crushing the black garlic and adding it I was concerned that because of how soft and mellow it is that it may not have the same effect in the slow-cooker. Should I add more black garlic to make up for how long it will be in the slow-cooker (maybe add it toward the end?) or should it be fine with a one-to-one substitution?
Black garlic is not a substitute for regular garlic, you add black garlic to get a different result. I would never say use 2 cloves of black garlic for every 1 regular or any other ratio because the changes are so fundamental that they really are totally different ingredients. 

The question is how much black garlic flavor you want, and only you can answer that. I'd suggest that you taste it when it's close to being done and if you want more add more then.