Drain the pumpkin by spreading it out on a few layers of paper towel and allowing it to sit for 10 minutes or so to remove some of the excess moisture.
Combine the warm water, honey and yeast in a large bowl. Let stand for 5–10 minutes, until foamy.
add the pumpkin purée and olive oil and stir to combine.
Add the flour and salt and mix with the dough hook on an electric mixer for 4-5 minutes.
Cover and allow to rise 30 minutes. Stretch and fold with wet hands.
Leave another 30 minutes. Stretch and fold again.
Let rise another 30 minutes.
Generously coat a 9×13-inch baking pan with 2-3 Tbsp olive oil. Transfer the dough to the pan and gently stretch it toward the corners. If it keeps springing back, let it rest for 10 minutes and try again.
Cover and let rise for another 45–60 minutes, until puffy.
Heat the oven to 425°F. Drizzle the dough generously with olive oil, then press your fingertips deeply into the dough, all the way down to the bottom of the pan.
Tuck the sage leaves into some of the dimples and sprinkle generously with Parmesan and flaky salt. Drizzle with a little more olive oil.
Bake for 22–28 minutes, until deeply golden on top and crisp around the edges.
Let it cool for at least 15 minutes before slicing.