Mediterranean Burgers

Name: Mediterranean Burgers
Ingredients: 4 sun-dried tomatoes, (not packed in oil); 1 1/2 cups vegetable broth, or water; 1/2 cup millet, rinsed (see Ingredient note); ¼ teaspoon salt; 6 teaspoons extra-virgin olive oil, divided; 1 large onion, chopped; 3 cups lightly packed baby spinach, stems trimmed; 2 cloves garlic, minced; Olive Ketchup, optional (recipe follows); ½ cup crumbled feta cheese; 1 tablespoon chopped fresh basil; ⅔ cup fine dry breadcrumbs; ¼ teaspoon freshly ground pepper; 7 whole-wheat English muffins, or whole-wheat buns; Arugula & sliced tomatoes, for garnish