Slice off the neck of the squash, and peel the round bottom piece with a knife.
Divide the bottom piece in half, top to bottom and remove the seeds.
Cut the squash into ¼” thick half-moon pieces.
Peel the neck pieces and slice into ¼” thick circles.
Combine the squash pieces and 2 oz. of oil in a mixing bowl. Season to taste with salt and pepper.
Spread the squash in a single layer on a parchment-lined sheet pan and bake in a 350°F oven for 10-12 minutes, or until tender. Allow to cool.
Whisk the eggs and a small amount of water in a mixing bowl.
Portion the squash into 6 oz. servings, using 2 round and 2 half-moon pieces per serving.
Slice the puff pastry in half once widthwise and in half once lengthwise to yield four rectangles.
Spread 1 oz. of duxelles on a round piece of squash. Place the squash, mushroom-side down, on top of the pastry. Repeat with a second round piece of squash and place atop the first piece. Reserve remaining squash for future recipes.
Press down on squash circles slightly, and wrap 2-3 half-moon pieces around the round pieces.
Brush egg wash on the edges of the pastry and pull the 4 corners of the pastry toward the centre of the squash. Press lightly to secure corners. Pull the short sides of the pastry toward the centre and press to seal.
Slice a second piece of pastry into ¼”x6” strips. Egg wash one side of 2 strips.
Wrap and crisscross the strips around the filled pastry.
Store the Wellingtons in a container lined with floured parchment paper. Cover and refrigerate until needed, up to 2 days.
Place the other vegetables in separate storage containers and refrigerate until needed, up to 2 days.
Boil a pot of salted water and add 5 lb. of cippolini onions.
Cook for 30-45 seconds, then drain, spreading the onions out to cool.
Peel the skins from the onions and trim both ends.
Drizzle 4 oz. of olive oil over the onions in a mixing bowl, adding in the rosemary and garlic. Season with salt and pepper to taste.
Bake in a 350°F oven for 10-12 minutes or until browned and tender. Cool and place in a covered storage container and refrigerate until needed, up to 2 days.
TO PREPARE À LA CARTE:
Slice a quarter piece of the Wellington horizontally.
Heat a sauté pan and add 1 Tbsp. of oil, broccoli, cippolinis and mushroom duxelles. Season with salt and pepper to taste.
Sauté the vegetables until browned and tender. Add 3 cippolini onions. Cook until just warmed through. Add the parsley and toss the pan to coat the vegetables.
Plate two halves of the Wellington on the sauce, with sliced side facing out. Place the onions next to the Wellington. Add the vegetables next to the Wellington.