Heat vegetable oil in a large skillet over medium-high heat until shimmering. Working in batches to avoid crowding, sear the beef pieces for 2-3 minutes per side until deeply golden brown. This crucial browning step develops rich flavor complexity through the Maillard reaction—don't skip it, even though it takes extra time.

Transfer the seared beef to your slow cooker and add the minced garlic, fresh ginger, soy sauce, rice vinegar, honey, sesame oil, and red pepper flakes. Stir thoroughly to combine, ensuring all beef pieces are coated with the aromatic sauce. Cover and cook on LOW for 5 hours and 45 minutes, allowing the meat to become incredibly tender.

In a small bowl, whisk together the cornstarch and beef broth until completely smooth with no lumps visible. This elegant slow cooker beef and broccoli recipe depends on this thickening slurry for the proper sauce consistency. Set aside until needed in the final stages.

During the final 15 minutes of cooking, add the broccoli florets directly to the slow cooker. This timing ensures the florets remain vibrant green and maintain a tender-crisp texture rather than becoming mushy. Stir everything together gently.

Pour the cornstarch slurry into the slow cooker while stirring constantly to distribute it evenly throughout. Cook uncovered for the final 15 minutes until the sauce thickens to a glossy, restaurant-quality consistency that coats the back of a spoon beautifully.

Turn off the slow cooker and taste for seasoning adjustments—you can add more soy sauce for saltiness or rice vinegar for brightness. Garnish generously with sesame seeds and sliced green onions just before serving to preserve their fresh flavor and textural contrast.