Roast the gram flour in a dry pan over medium heat for 3-4 minutes until golden and aromatic. Mix with 1/2 cup water to form a smooth paste. Set aside.
Heat vegetable oil in a large pot over medium-high heat. Add chopped onions and sauté for 5-6 minutes until golden brown.
Add ginger-garlic paste and cook for 2 minutes until fragrant, stirring continuously.
Add turmeric powder and red chili powder, mixing well. Cook for 30 seconds.
Add chicken pieces and stir to coat with spice mixture. Cook for 5-7 minutes until lightly browned.
Pour in stock and bring to a boil. Reduce heat to medium-low and simmer for 15 minutes until chicken is cooked through.
Slowly add the gram flour paste while stirring continuously to prevent lumps. Simmer for 5 minutes to thicken.
Pour in coconut milk and add fish sauce. Stir well and simmer for 10 minutes on low heat. Adjust salt to taste.
Cook noodles according to package instructions in a separate pot. Drain well.
Serve noodles in bowls, ladle curry over them, and offer all condiments (eggs, fried onions, cilantro, peanuts, lime, crispy noodles) for customization.
Notes
Store curry base separately from noodles. Gram flour can be found in Indian grocery stores. Adjust spice level to taste. Can be made vegetarian by substituting chicken with tofu and vegetables.