1. Coat a 10- by 15-inch pan generously with cooking oil spray. Peel potatoes and cut lengthwise into 1/4-inch-thick sticks. In pan, mix potatoes with 1/2 tablespoon olive oil. Sprinkle with 1/4 teaspoon paprika, 1/4 teaspoon salt, and 1/8 teaspoon pepper; mix and spread level. Bake in a 450 degree regular or convection oven, turning occasionally with a wide spatula, until potatoes are crisp and browned on the outside and tender to bite on the inside, 25 to 30 minutes.
2. Meanwhile, in a 4- to 5-quart pan over high heat, stir onion, carrots, celery, thyme, curry powder, and remaining 1/4 teaspoon paprika in remaining 1/2 tablespoon olive oil until vegetables are limp, about 5 minutes. Add wine and tomatoes and their juices; boil, stirring occasionally, to blend flavors, about 5 minutes. Stir in crème fraîche and season to taste with salt and pepper.
3. Discard any gaping mussels that don't close when you tap their shells. Add mussels to pan; cover and cook until shells pop open, 8 to 10 minutes.
4. Ladle mussels and broth into wide bowls. Serve with oven frites.