Steamed Clams and Kale

Name: Steamed Clams and Kale
Ingredients: 3 tablespoons unsalted butter; 1 white onion, halved and thinly sliced; 2 cloves garlic, thinly sliced; 1 tablespoon tomato paste; 1/2 teaspoon hot Spanish paprika, plus more for sprinkling; 1/4 teaspoon dried oregano; 1 1/4 cups dry white wine; 1 8-ounce bottle clam juice or 1 cup vegetable broth; 3/4 pound small red-skinned potatoes, halved; 40 littleneck clams (3 to 4 pounds), scrubbed; 1 bunch kale (preferably Tuscan kale), leaves roughly chopped; Crusty bread, for serving (optional)