Toast the oats and walnuts on a sheet pan for 15 minutes in a 350ºF oven. Cool briefly before combining with the remaining ingredients.
Add the pitted dates to a food processor and pulse a few times before adding the cooled toasted oats/nuts and pulse a few more times. Then add the almond butter, cocoa powder, syrup, and salt. Pulse a few more times. You don't want to make a smooth puree, just an evenly mixed granola-like blend.
Place the mixture in a parchment lined dish and press into an even layer. Refrigerate for 30 minutes. (I used a 1/8 sheet pan that measures about 6.5"x9.5" for the bars pictured here. I've also used a 1/4 sheet pan that measures closer to 9"x13". Would you rather have thin or thick granola bars?)
After 30 minutes, melt the chocolate and olive oil together in a saucepan over low heat. Pour the melted chocolate over the pressed granola and spread it around. Carefully smack the dish on a flat surface to make sure it's evenly distributed.
Refrigerate for at least an hour before slicing. Optional: Sprinkle flaky salt over the bars 20-30 minutes into the chocolate setting.
The bars should keep in an airtight container inside the refrigerator for up to a month.