How to Make It
In a small saucepan, combine the water, salt, butter and paprika and bring to a boil. Pour the mixture into a large bowl and let cool to room temperature. Stir in the 3 3/4 cups of flour until the dough comes together. On a lightly floured work surface, gently knead the dough until smooth. Wrap the dough in plastic and refrigerate until firm, about 1 hour.
In a saucepan of boiling salted water, cook the spinach for 1 minute. Using a slotted spoon, transfer the spinach to a colander. Add the fava beans to the boiling water and cook until bright green, 1 minute. Using a slotted spoon, transfer the fava beans to a plate. Add the green beans to the boiling water and cook until tender, 4 minutes. Drain and finely chop the green beans. Peel the tough outer skins from the fava beans. Squeeze the excess water from the spinach, then coarsely chop it.
In a large skillet, melt the butter in the olive oil. Add the onion and cook over moderate heat, stirring occasionally, until softened, about 10 minutes. Add the garlic and cook until fragrant, about 3 minutes. Stir in the spinach, fava beans, green beans and peas and cook, stirring, until heated through, about 2 minutes. Stir in the mint and thyme and season with salt and pepper.
Preheat the oven to 350°. Lightly oil 2 large baking sheets. On a floured work surface, roll out the dough 1/8 inch thick. Using a 3 1/2-inch round biscuit cutter, cut out 32 rounds from the dough. Moisten the edge of 1 dough round with water. Mound 1 tablespoon of the vegetable filling on half of the round and fold the other side over. Press to seal the dough and pinch at intervals to make pleats. Repeat with the remaining dough rounds and filling.
Arrange the empanadas on the prepared baking sheets and bake in the upper and lower thirds of the oven for about 30 minutes, until browned. Serve the empanadas warm or at room temperature.