Roasted Cabbage Steaks With Crispy Chickpeas and Herby Croutons

Name: Roasted Cabbage Steaks With Crispy Chickpeas and Herby Croutons
Ingredients: 2 medium purple or green cabbages (4–5 lb. total; second cabbage optional); 2 tsp. (or more) kosher salt, divided; 1 3/4 tsp. freshly ground black pepper, divided; 2 (14.5-oz.) cans chickpeas, drained, rinsed; 1 tsp. ground cumin; 1/2 cup plus 1 Tbsp. extra-virgin olive oil, divided; plus more for drizzling; 1 1/4 tsp. ground coriander, divided; 1/2 loaf sourdough bread (about 1/2 lb.); 2 garlic cloves, finely grated, divided; 2 tsp. Dijon mustard, divided; 2 Tbsp. finely chopped parsley, plus whole leaves for serving; 1/2 cup vegan or regular mayonnaise; 2 Tbsp. (or more) fresh lemon juice