Heat the avocado oil in a large Dutch oven or heavy-bottomed pot over medium-high heat. Add the beef in a single layer (working in batches if needed) and sear until well browned on all sides. Transfer the beef to a plate.
Carefully pour off and discard most of the fat from the pan, leaving just a thin coating.
Reduce the heat to medium and add the Challenge Unsalted Butter (1 cube). Once melted, add the sliced onion and cook, stirring occasionally, until very soft and lightly caramelized, about 8–10 minutes.
Add the garlic and ginger and cook for about 30 seconds, just until fragrant.
Return the beef to the pot along with any accumulated juices. Add the stock, soy sauce, and brown sugar or honey. Stir well, scraping up any browned bits from the bottom of the pot.
Bring the stew to a gentle simmer. Reduce the heat to low, cover, and cook for 40 minutes, until the beef is tender and the broth is flavorful.
Add the squash and continue to simmer, uncovered, for 15–20 minutes, until the squash is tender but still holding its shape.
Stir in the lemon zest and juice. Season with black pepper and adjust sweetness or soy sauce to taste. Serve with steamed rice to soak up the broth.
Finish with whatever you like or have on hand: sliced scallions, chili crisp, toasted sesame seeds, or a drizzle of sesame oil.
Serve with steamed rice to soak up the broth.
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