Peel one 1 butternut squash, then cut the “snout” into 1 inch chunks to make 3 C. Simmer the chunks in 3 C. whole milk for 10 minutes or until quite tender.
Grease the bottom and sides of a large cast iron skillet with butter.
Drain the butternut squash and discard the milk. Place in a large bowl and use a hand blender or whisk to puree it.
Cut the bulb end of the peeled squash in half and scoop out the seeds and pulp. Slice each half into half-rounds. If they are more than 3 inches long, cut them in half.
In a non-stick 12 inch pan, heat 1/2 C. granulated sugar and 1/2 C. water. Stir with a wooden spoon until the mixture begins to bubble and then brown –about 6 minutes. Add squash slices in a single layer, nesting them together to cover as much of the pan as possible.
Cook the squash in the caramel for 8-10 minutes, until it is nicely browned on one side. Add 1/4 C. more water any time the mixture starts to get too thick. Flip the squash slices and cook another 8-10 minutes, adding water as necessary but letting the caramelize thicken.
Pour the caramel and squash into the cast iron skillet and arrange in a single layer.
Preheat the oven to 350.
In another bowl, beat together 1/2 C. salted butter and 1/2 C. turbinado sugar. Add 1/2 C. maple syrup and beat to combine. Add 3 eggs and beat them into the batter. Finally add the squash puree and 3 T. apple cider vinegar and mix well.
In yet another bowl, sift together 2 1/4 C. flour, 2 t, baking powder, 3/4 t. salt, 1/2 t. ground ginger and a pinch of nutmeg. Combine with the squash puree mixture by hand using a spatula, in as few strokes as possible.
Pour the batter over the caramelized squash, using the spatula to spread it evenly and fill the pan completely.
Bake until a toothpick inserted comes out clean. Allow to cool for 10 minutes before eating.