Preheat the oven to 400 degrees F.
For the toasted pita chips: Combine the cumin, za'atar, chile powder and granulated garlic in a small bowl. Brush the pitas on both sides with the olive oil; cut each pita into 8 triangles. Toss the pita wedges in the spice mixture until fully coated, then spread them out on a baking sheet. Toast in the oven until golden brown and crispy, 14 to 16 minutes. Let cool on a paper-towel-lined plate.
For the white bean-tahini puree: Lay the anchovies on a small baking sheet and place in the oven for 6 to 8 minutes.
In a large saute pan over medium-high heat, add the olive oil, garlic, cannellini beans and roasted anchovies. Cook, stirring often, for 4 to 6 minutes; transfer to a food processor along with the tahini, chicken stock, salt, red pepper flakes, black pepper and lemon juice and zest. Process until smooth and creamy. Transfer the puree to a bowl and garnish with the chives. Serve immediately with the toasted pita chips.