Creamy Tahini and Harissa Beef

Name: Creamy Tahini and Harissa Beef
Ingredients: ½ cup well-mixed tahini; 2 Tbsp. fresh lemon juice; 1½ tsp. Diamond Crystal or ¾ tsp. Morton kosher salt, divided, plus more; 2 Tbsp. vegetable oil; 1 large red onion, finely chopped; 6 scallions, white and pale green parts and dark green parts separated,thinly sliced; 8 garlic cloves, coarsely chopped; ¾ cup harissa (preferably thick); 1 tsp. crushed red pepper flakes (optional); 1 lb. ground beef (20% fat); 1 7–8-oz. bag salted pita chips; ½ cup coarsely chopped mixed tender herbs (such as parsley, cilantro, and/or mint)