Kabocha Squash Focaccia with Gruyere, Caramelized Onion & Sage

1 ¼-oz. envelope active dry yeast (about 2¼ tsp.)
2 tsp. honey
5 cups (625 g) hard red wheat flour (see note below)
1 tablespoon pink Himalayan salt
6 Tbsp. extra-virgin olive oil, divided, plus more for hands
4 Tbsp. unsalted butter, divided
1 medium onion
1 kabocha squash
4 oz gruyere, coarsely grated
12-18 sage leaves
Flaky sea salt

Prepare the dough: 
Whisk one ¼-oz. envelope active dry yeast (about 2¼ tsp.), 2 tsp. honey, and 2½ cups lukewarm water in a medium bowl and let sit 5 minutes (it should foam or at least get creamy; if it doesn’t your yeast is dead and you should start again—check the expiration date!).

Add 5 cups (625 g) flour and 1 tablespoon salt and mix with a rubber spatula until a shaggy dough forms and no dry streaks remain.

Pour 4 Tbsp. extra-virgin olive oil into a big bowl that will fit in your refrigerator. This puppy is going to rise! Transfer dough to bowl and turn to coat in oil. Cover with a silicone lid or plastic wrap and chill until dough is doubled in size (it should look very bubbly and alive), at least 8 hours and up to 1 day. If you're in a rush, you can also let it rise at room temperature until doubled in size, 3–4 hours.

While the dough is rising, prepare the toppings.

Squash: 
-Heat the oven to 350º
-Cut the squash in half, scoop out the seeds
-Drizzle the inside with a little olive oil and place on a sheet pan cut side down
-Bake for about 45 minutes or until tender and creamy, remove from oven and let cool
-Scoop out all the squash and set aside until ready to bake. 

Onions: 
-Cut the onion in 1/2 and slice into 1/2 rounds
-Heat a skillet to medium high, add 2 tablespoons olive oil
-Add onions and cook for a couple of minutes until you see a little browning.
-Season the onions with a hearty pinch of salt.
-Turn the heat down to low, add 2 tablespoons of butter and continue to cook stirring occasionally to prevent burning, for about 30-40 minutes, or until they turn a deep golden brown color and become soft and caramelized.

Gruyere:
-grate using a course grater

Sage:
-melt the remaining 2 tablespoons of butter and dip all the sage leaves in the butter. You can leave them resting in the butter until ready to use. 

Bake the focaccia:
Generously oil a 13x9" baking pan. Keeping the dough in the bowl and using a fork in each hand, gather up edges of dough farthest from you and lift up and over into center of bowl. Give the bowl a quarter turn and repeat process. Do this 2 more times; you want to deflate dough while you form it into a rough ball. Transfer dough to prepared pan. Pour any oil left in bowl over and turn dough to coat it in oil. Let rise, uncovered, in a dry, warm spot (like near a radiator or on top of the fridge or a preheating oven) until doubled in size, at least 1½ hours and up to 4 hours.

Place a rack in middle of oven; preheat to 450°. To see if the dough is ready, poke it with your finger. It should spring back slowly, leaving a small visible indentation. If it springs back quickly, the dough isn’t ready. (If at this point the dough is ready to bake but you aren’t, you can chill it up to 1 hour.) Lightly oil your hands. Dimple focaccia all over with your fingers, like you’re aggressively playing the piano, creating very deep depressions in the dough (reach your fingers all the way to the bottom of the pan).

Now you can start adding your toppings, starting with the gruyere. Sprinkle it all over the dough evenly. Next add the caramelized onions and scatter them around evenly. Scatter the kabocha squash around in little chunks. Finally, dip each sage leaf in the melted butter and scatter on top of the squash. Once all the sage has been dipped drizzle the remaining butter on top. Sprinkle with flaky salt. 

Bake focaccia until puffed and golden brown all over, 20–30 minutes.