Prepare the pan. Generously coat the bottom and sides of a 9 × 13-inch metal baking pan with approximately 2-inch sides with 2 tbsp olive oil. Do not use a baking sheet for this version.
Mix the dry ingredients. In the bowl of a stand mixer, thoroughly whisk together the GF bread flour, milk powder, yeast, salt, sugar and ascorbic acid. Take a little extra time here to ensure the ascorbic acid is evenly dispersed.
Add the liquids. Whisk together the squash purée, 510 g warm water and 54 g olive oil and 2 tsp vinegar until smooth. Pour into the dry ingredients. Using the paddle attachment, mix on low until incorporated. Increase to medium and beat for 4–5 minutes. Add the garlic and herbs during the final minute. The dough should be very soft, sticky and hydrated—much softer than conventional bread dough. It should slowly slump from the paddle and absolutely should not form a firm kneadable ball.
If it still appears stiff after the full mixing time, add additional warm water 1 tbsp (15 g) at a time, mixing thoroughly between additions. Don’t add extra flour.
Transfer to the pan. Using an oiled spatula, gently transfer the aerated dough to the prepared pan without punching it down. Drizzle your fingertips with olive oil and gently coax the dough toward the corners. Avoid aggressively flattening it.
Rise. Drizzle the remaining olive oil generously over the surface. Coat your fingertips with oil and press deeply into the dough to create irregular dimples. Be somewhat restrained—we want to preserve the gas pockets created during proofing. Cover loosely and proof for 45–75 minutes, or until noticeably puffy, aerated and approximately 50–75% larger. The surface should show some bubbling, and the dough should have a gentle jiggle when the pan is moved.
Toward the end of the rise, preheat the oven to 425°F (220°C) with a rack positioned slightly below center.
Bake. Bake for 20 minutes before checking. Continue baking as necessary, approximately 25–30 minutes total, until the top is deeply golden, the edges are browned and crisp, and the center registers approximately 205–208°F (96–98°C). Do not continue baking simply to reach the stated time. If it reaches temperature and has good color earlier, remove it.
Cool. Allow the focaccia to rest in the pan for 5–10 minutes, then carefully transfer it to a wire rack.
Cool for at least 20 minutes before cutting or tearing.
Dip. Add the ricotta, squash purée, parmesan, olive oil, maple syrup, roasted garlic, sage, thyme, salt, pepper and nutmeg to a food processor. Process for 1–2 minutes, scraping down the bowl as necessary, until exceptionally smooth, creamy and aerated. Spoon into a shallow serving bowl and create loose swirls with the back of a spoon.
