Heat canola oil in a medium saucepan over medium-high heat.
Add garlic paste and ginger paste; cook, stirring constantly, until fragrant, about 1 minute.
Add tomato paste; cook, stirring constantly, until slightly darkened, about 1 minute.
Stir in broth, cinnamon stick, star anise and peppercorns; cover and bring to a boil over high heat.
Reduce heat to medium to maintain a simmer; simmer for 10 minutes.
Stir in butter and fish sauce, whisking to melt the butter completely.
Meanwhile, bring a large pot of water to a boil.
Cook noodles according to package directions. Drain.
Divide the noodles among 4 shallow bowls.
Ladle 1 cup of the broth over each; drizzle each bowl with 1 teaspoon sesame oil.
Sprinkle with scallions and sesame seeds.
