In a pot over medium heat, heat oil. Add potatoes and cook for about 3 to 4 minutes or until lightly browned and tender. Remove from pan and drain on paper towels.
Add carrots and cook for about 1 to 2 minutes. Remove from pan and drain on paper towels.
Remove excess oil from pot except for about 2 tablespoons. Add beef in a single layer and sear for about 2 to 3 minutes on each side.
Add onions, garlic, and ginger and cook until softened.
Add fish sauce and continue to cook for about 2 to 3 minutes.
Add water and bring to a boil, skimming scum that floats on top. Lower heat, cover and simmer for about 1 to 1 ½ hours or until beef is tender.
Add coconut milk and continue to simmer until liquid is slightly reduced.
Add potatoes and carrots and cook for about 3 to 5 minutes or until fork-tender.
Add curry powder and cook, stirring to combine, for about 3 to 5 minutes or until sauce starts to thicken. Season with salt and pepper to taste.
Add bell peppers and cook for about 1 minute or until tender yet crisp.
Serve hot.