Quick and Easy Udon Noodle Soup

Name: Quick and Easy Udon Noodle Soup
Ingredients: 2 teaspoons cooking oil; 8 oz cremini or white mushrooms (sliced or *see Note 1 for alternatives); salt and pepper; 1 clove garlic (thinly sliced); 1/2 teaspoon ginger paste (or 1/4 tsp freshly grated ginger); Pinch red pepper flakes (optional); 4 cups chicken or other broth (*see Note 2 for alternatives); 2 Tablespoon soy sauce (can add more, to taste); 2 teaspoon fish sauce (or mirin); 2 teaspoon sesame oil; 14 oz frozen or shelf-stable udon noodles (2 blocks frozen or 2 individual packages of shelf stable 400-500g total); 2 cups baby spinach (and/or other greens *see Note 3 for other options); 1 green onion (thinly sliced, plus more for garnish); 1/4 cup cilantro (leaves and tender stems, coarsely chopped); 1-2 teaspoon Asian chili garlic sauce (plus more, to taste (optional) *see Note 4 for alternatives); Juice of 1/2 lime + lime wedges to serve; Additional salt (as needed)