:::For the Dough:1 cup whole milk, heated to 115°:::
2¼ teaspoons (¼ ounce) active dry yeast
¼ teaspoon sugar
5 cups flour
1 cup water
⅓ cup extra-virgin olive oil, plus more for greasing and brushing
2 teaspoons kosher salt
:::For the Topping:4 tablespoons butter:::
6 medium (3½ pounds) yellow onions, thinly sliced
4 thyme sprigs
3 bay leaves
Kosher salt and freshly ground black pepper, to taste
¼ cup oil-cured kalamata olives, halved
10 oil-cured anchovy fillets
Directions
Make the dough: In the bowl of stand mixer fitted with a dough hook attachment, combine the heated milk with the yeast and the sugar. Let sit until starting to foam, 10 minutes. To the milk mixture, add the flour, water, olive oil and salt, and mix until a smooth dough comes together, 5 to 6 minutes. Cover the bowl with a kitchen towel and let sit in a warm area until it's doubled in size, 1 hour.
Meanwhile, prepare the topping: In a large skillet, melt the butter over medium heat. Add the onions, thyme and bay leaves, and cook, stirring often until soft and golden brown, 35 to 40 minutes. Season with salt and pepper. Transfer to a bowl and let cool slightly, then discard the herbs.
Transfer the dough to a greased baking sheet and press to fit the entire surface of the pan. Spread the onion mixture on top, then arrange the olives and anchovies. Lightly cover in plastic wrap and let proof until puffed, another 30 minutes. Preheat the oven to 400º.
Transfer the tray to the oven and bake until golden brown, 25 to 30 minutes. Let cool completely, then slice and serve.