1 teaspoon safflower oil or corn oil

2 tablespoon shallots, minced

2 tablespoons lemon grass, 2 stalks lemongrass, trimmed, wilted (or tough outer leaves discarded), cut into 2-inch lengths, and smashed lightly with the flat side of a knife

1 whole ripe tomato, large, cored, seeded, and cut into 1/4-inch thick wedges

1/2 lb button mushrooms, rinsed, drained, stems trimmed, and caps thinly sliced

1-1/2 tsp sugar

5 cups water

½ lb fresh shrimp, medium shrimp, peeled, scored down the back, deveined, and rinsed

5-1/2 tbsp fish sauce

3 tablespoons fresh mexican lime juice

4 oz rice noodles, very thin rice stick noodles (vermicelli) softened in hot water and drained

1-1/2 cups bean sprouts, rinsed and drained

½ teaspoon Crushed red pepper

2 each Fresh scallions, ends trimmed, finely minced scallion greens