Instructions

• Preheat the oven to 300°F and place a rack in the middle position. Pour ½ cup olive oil into a small baking dish or oven-safe bowl. Place the garlic head halves cut side down in the oil, cover the dish tightly with foil, and roast until the garlic is tender and golden, 45–60 minutes.
• Remove the dish from the oven. Carefully pour the hot oil through a fine-mesh strainer into a clean heatproof bowl. Using a spoon or tongs, press the roasted garlic cloves out of their skins into the bowl and reserve the cloves. Discard the skins and any solids caught in the strainer. Let the roasted garlic oil cool completely before using.
• Rinse and thoroughly dry the bowl of a stand mixer. Sprinkle the envelope (2 ¼ teaspoons) active dry yeast into the bowl, then pour in 1 ¾ cups warm water. Stir gently to dissolve and let sit 3–5 minutes, until the mixture is foamy.
• Fit the mixer with the dough hook and start on low speed. Add 4 cups white flour, 2 teaspoons fine-grain sea salt, and 2 tablespoons of the cooled roasted garlic oil. If needed, add the flour in two additions so the mixer can handle it.
• Increase the mixer to medium once the dough begins to come together. Stop occasionally to scrape dough off the hook. Mix until the dough is smooth and slightly sticky, about 8–10 minutes.
• Add 2 teaspoons of roasted garlic oil to a large bowl and spread it around. Transfer the dough ball to that bowl and turn it so all sides are coated in oil.
• Cover the bowl with a clean kitchen towel and set it in a warm, draft-free spot to rise until doubled in size, about 1 hour 45 minutes.
• Lightly oil a rimmed baking sheet with 1 teaspoon roasted garlic oil, spreading it over the bottom and sides.
• When the dough has doubled, uncover and punch it down. Transfer the dough to the prepared baking sheet and gently stretch and press it to fill the pan to the edges.
• Cover the pan with a clean tea towel and let the dough rest in a warm spot for 30 minutes. While it rests, preheat the oven to 450°F.
• Uncover the dough. Grease your fingertips with roasted garlic oil and dimple the surface of the dough all over.
• Brush the surface with additional roasted garlic oil, dot with the reserved roasted garlic cloves, then sprinkle evenly with just under 2 tablespoons coarsely chopped fresh rosemary (from 3–4 sprigs) and a few pinches of flaky sea salt.
• Place the pan in the oven and immediately reduce the oven temperature to 375°F. Bake until the focaccia is golden brown, 20–25 minutes.
• Transfer the baked focaccia to a wire rack and let cool slightly before slicing and serving.