Soak skewers in water for 30 minutes. Drain, pat dry. Thread Beef Tenderloin Tips onto each wooden skewer. Cover with plastic wrap and refrigerate until needed.
To make the sauce, bring a small pan of water to a boil. Add garlic cloves and blanch them in boiling water for 30 seconds to a minute. Drain the cloves, pat them dry and chop finely. In a small skillet, melt 2 tbsp. of butter over medium-high heat. Add the garlic, ginger, and green onion and sauté just until they begin to soften and smell fragrant, about 2 minutes. Add chicken stock, soy sauce, honey, hoisin sauce and chili flakes and bring to a boil. Cook for 1 to 2 minutes. Pour the sauce through a strainer into a clean pan and, over medium heat, whisk in the remaining 2 tablespoons of butter, a little bit at a time. Set aside and keep warm.
Preheat outdoor grill. Grill the skewers until cooked through and nicely browned, about 2 minutes per side (1 minute if you want the meat rare). Transfer to a platter, pour on the sauce, and serve; or serve with the sauce on the side for dipping.