Black Pepper Beef and Broccoli Noodles

Name: Black Pepper Beef and Broccoli Noodles
Ingredients: 1 cup / 240ml Beef Stock; 2 tbsp Oyster Sauce; 2 tbsp Dark Soy Sauce; 1 tbsp White Rice Vinegar; 1 packed tbsp Brown Sugar; 1 tbsp Cornstarch/Cornflour; 1x 9-10oz/250-300g head of Broccoli, (diced into bite sized pieces ); 10oz / 300g Steak, (sliced into thin strips (see notes)); 2x 5oz/150g packs of Udon Noodles ((straight to wok noodles)); 2 tsp Black Pepper ((see notes)); 1 medium White Onion, (sliced into thin strips); 2 cloves of Garlic; 1 tsp Ginger, (finely grated/diced); 1 tbsp Sesame Oil; Vegetable Oil, (as needed); finely sliced Spring Onion; Sesame Seeds