Step 1

Combine the water and yeast in the bowl of a stand mixer fitted with the hook attachment and let stand until the yeast is dissolved, about 5 minutes. Add the milk, eggs, sugar, and salt, and mix until combined. Add 4 1/2 cups of the flour and knead on low speed until a shaggy dough forms. Continue kneading on low speed until the dough comes together and is no longer floury, about 5 minutes. Begin adding the butter one piece at a time, waiting until one piece is just barely incorporated before adding the next.

Step 2

When all the butter has been added, continue kneading for another 5 minutes until the dough is silky and elastic. It will bunch around the dough hook but won’t form a smooth ball; that is okay. Add the remaining 1/4 cup of flour as needed if the dough is sticking to the sides of the bowl.

Step 3

Coat a large bowl with more butter. Transfer the dough into it, cover with plastic wrap or a clean kitchen towel, and let rise until doubled in size, 1 to 1 1/2 hours.

Step 4

Stir the ricotta, pesto, and Parmesan together in a medium bowl until combined.

Step 5

Line 2 (8x4-inch) loaf pans with long rectangles of parchment paper so that the parchment hangs over the long sides of the pan. Grease the pans with butter or cooking spray.

Step 6

When the dough is ready, sprinkle a work surface lightly with flour and place the dough on top of it. Divide into 2 pieces.

Step 7

Roll one of the pieces of dough into a 10x14-inch rectangle with the short end facing you. Spread half the filling on top in an even layer, leaving a 1-inch border. Top with half of the sun-dried tomatoes.

Step 8

Starting with the short end closest to you, carefully roll the dough into a log. If the dough sticks to the counter, use a bench scraper to gently pry it up. When done rolling, pinch the dough to seal it closed and arrange seam-side down. Gently cut the log lengthwise, creating two halves with lots of layers.

Step 9

Position the halves so that the layers are facing up. Press the two halves together at one end, then twist the halves around each other, creating a spiral. Press the halves together again at the other end. Carefully transfer the loaf into a loaf pan. If the loaf is a little too long for the pan, just smoosh it a little on either end to make it fit.

Step 10

Repeat with the other piece of dough to create a second loaf. Cover the loaves with plastic wrap or clean kitchen towels and let them rise on the counter until puffed, about 1 hour.

Step 11

Arrange a rack in the middle of the oven and heat to 350°F. Whisk the egg with 1 teaspoon water and gently brush it all over the surface of the loaves. Top with a sprinkling of grated Parmesan, several grinds black pepper, and flaky sea salt. Bake until golden-brown and a skewer inserted in the center comes out clean, 45 to 55 minutes.

Step 12

Let the loaves cool in the pan for about 20 minutes. Run a knife around the edges to release them from the pan. Use the parchment to lift the loaves from the pan. Place them on a wire rack and slide the parchment out from underneath. Serve warm.