Slow Cooked Buttery Spinach and Beans

Name: Slow Cooked Buttery Spinach and Beans
Prep time: 10 min
Cook time: 2 h 15 min
Total time: 2 h 25 min
Cuisine: European
Ingredients: 550 grams frozen spinach (approximately 4 cups of frozen spinach); 400 grams presoaked beans (or 1 large can around 400 grams / 15 oz); 1 medium yellow onion (sliced into rings); 10 tablespoons butter; 8 cloves garlic; 2 tablespoons no-sodium chicken bouillon (about 2 cubes, or substitute vegetable bouillon ); 2 teaspoons summer savory (or thyme); 1 teaspoon black pepper; 1.5 teaspoons salt; 3 cups water