For the Chicken: If cooking
Fill a 4-quart saucepan halfway with water. Bring the water to a boil. Add chicken. Return to a boil.
Partially cover with a lid. Lower the heat to maintain a simmer. Cook until chicken is tender and falling away from the bone (approximately 40 minutes).
Use tongs to transfer the chicken to a large bowl or platter. Allow the chicken to cool (approximately 15 minutes).
Strain the remaining stock through a fine-mesh strainer into a large metal pot. Set aside the strained stock (you should have about 1.4 liters).
Shred it into small pieces. Dispose of the skin and bones.
*Or you can use leftover chicken, or pork and skip this step, just make or thaw a liter of chicken broth for later
In a wok, heat oil over high heat until shimmering. Add garlic and onions and cook, stirring frequently, until softened and light brown in color, about 2 minutes.
Add Vegetables and cook, stirring frequently, until vegetables have brightened in color and are crisp-tender, about 2 minutes. Scrape stir-fried vegetables into a medium heatproof bowl; set aside.
For the Pancit Noodles: Add 2 cups of the reserved broth to the wok and bring to a boil over high heat. Add rice noodles, stirring to ensure that noodles are wet. Cook, stirring frequently, until noodles soften and turn translucent, about 3 minutes; if noodles have not hydrated , add more stock in 1/4 cup increments.
Return stir-fried vegetables to wok along with shredded chicken.Mix everything thoroughly. Lower heat to maintain a simmer. Add oyster sauce, soy sauce, and fish sauce. Stir until sauces are fully incorporated and noodles are coated in a saucy glaze.
Garnish with scallions. Serve immediately with calamansi or lemon wedges