To make coconut rice, add rice to a medium saucepan. Cover with coconut milk and water. Stir in salt and ginger root. Set to medium-high heat. When boiling, cover pot and lower heat to a simmer. Cook undisturbed until all the liquid is absorbed by the rice—about 18 minutes.
Use a fork to fluff and stir the rice. Discard the ginger and keep rice warm over lowest heat.
Season shrimp lightly with salt and pepper. Add oil to a large, non-stick skillet and set over medium heat. When shimmering, add mustard seeds, cinnamon stick and pepper. Stir until fragrant, about a minute.
Add in onion and garlic, stirring occasionally until softened, about 5 minutes. Pour in curry powder and tomato sauce. Stir well and bring to a gentle simmer. Add shrimp and cover; cook about 6 minutes, stirring once or twice, until shrimp are pink and opaque.
Stir in coconut milk and allow to cook over low heat another minute or two. Taste and season with additional salt if needed. Discard the cinnamon stick and jalapeño pepper. Serve curry with coconut rice and top generously with chopped cilantro and black pepper.