Soak sotanghon noodles in water for at least 10 minutes. When the noodles have softened cut them into shorter lengths using a pair of kitchen shears. Keep them in water and set aside.
Heat achuete oil in a large pot over medium-high heat.
Saute garlic until lightly browned. Add onions and saute until fragrant and softened.
Add carrots, cabbage, and shredded chicken breast.
Toss to coat chicken and vegetables with oil.
Add chicken stock.
Drain noodles and add them to the pot.
Add fish sauce.
Bring to a boil and simmer until vegetables and noodles are cooked.
Season with salt and freshly ground pepper to taste.
Garnish with green onions and chicharron and serve hot.