Add 10 cups hot water and 2 tsp salt to a large pot (use same for 4 ppl). Cover and bring to a boil over high heat. Core, then cut pepper into ¼-inch slices Separate bok choy leaves, then cut into 1-inch pieces.(TIP: Rinse bok choy leaves to wash away any hidden dirt!) Peel, then cut half the onion (whole onion for 4 ppl) into ¼-inch slices.
Heat a large non-stick pan over medium heat. When hot, add peanuts to the dry pan. (TIP: You can skip this step if you don't want to toast the peanuts.) Toast, stirring often, until golden-brown, 4-5 min. (TIP: Keep your eye on them so they don't burn!) Transfer peanuts to a plate. Add peanut butter and ¼ cup (½ cup) warm water to a medium bowl. Whisk until smooth. Add ginger sauce, honey-garlic sauce and half the beef stock powder. Whisk to combine.
Add linguine to the boiling water. Cook uncovered, stirring occasionally, until tender, 10-12 min. Reserve ¼ cup (½ cup) pasta water, then drain and return linguine to the same pot, off heat.
Meanwhile, heat the same pan (from step 2) over medium-high. When the pan is hot, add 1 tbsp (2 tbsp) butter, then swirl until melted, 30 sec. Add onions, bell pepper, bok choy and 1 tbsp (2 tbsp) water. Season with pepper and half the garlic salt, then stir to combine. Cover and cook, stirring occasionally, until tender-crisp, 3-4 min. Remove from heat. Transfer veggies to a plate, then cover to keep warm. Carefully wipe the pan clean.
Reheat the same pan over medium-high. When the pan is hot, add ½ tbsp (1 tbsp) oil, then beef and pork mix. Season with remaining garlic salt, remaining beef stock powder and pepper. Cook, breaking up meat into smaller pieces, until no pink remains, 4-5 min.** Add sauce mixture. Bring to a simmer. Cook, stirring often, until sauce is warmed through and fragrant, 1 min.
Add meat mixture and veggies to the pot with linguine. Season with salt and pepper, then toss to combine. Cook, stirring occasionally, until linguine and veggies are warmed through, 1-2 min. (TIP: For a lighter sauce, add reserved pasta water, 1-2 tbsp at a time, until desired consistency is reached.) Divide linguine and any remaining sauce in the pot between plates. Sprinkle peanuts over top.