1/4 cup [30 g] roughly chopped hazelnuts
4 Tbsp [55 g] unsalted butter
1 acorn squash, halved and seeded
1/4 cup [60 ml] water
1 Tbsp dark brown sugar
1 tsp chopped fresh rosemary leaves
1/2 cup [120 ml] Vegetable Stock (page 222)
1/2 tsp fresh lemon juice
Freshly ground black pepper
In a small, dry frying pan over medium heat, toast the hazelnuts until fragrant, about 3 minutes. Set aside and let cool.
Preheat the oven to 425°F [220°C].
In a small saucepan over medium heat, melt and cook the butter, skimming the solids from the surface until the butter is clear. Turn the heat to low, and cook until the butter develops a nutty aroma and turns from yellow to a deep brown. Remove from the heat and let cool. (Store in an airtight container in the refrigerator for up to 3 weeks.)
Put the squash halves in a large roasting pan, cut-side down. Add the water to the pan, cover with aluminum foil, and roast for 25 minutes. Remove the foil, and continue roasting until the squash is lightly browned, about 10 minutes longer. Cut the squash halves into bite-size pieces and transfer to a serving platter.
In a small sauté pan over medium-high heat, warm the brown butter. Add the toasted hazelnuts and brown sugar and season with salt. Stir in the rosemary and cook until the rosemary becomes fragrant and the sugar has dissolved into the butter, about 3 minutes. Add the stock, a little bit at a time, and continue to cook until you have an emulsified, slightly thickened pan sauce. Remove from the heat and stir in the lemon juice.
Pour the brown butter sauce over the squash and season with pepper. Serve warm.