Prepare your protein source. If making homemade seitan, cook and slice into strips. For baked tofu, chop into cubes after pressing out excess moisture.

In a large skillet or wok, heat 2 tablespoons of sesame oil over medium heat. Add the chopped yellow onion and sauté for about 5 minutes until translucent.

Stir in the chopped broccolini with a splash of water. Cook for about 6–8 minutes until softened.

In a bowl, combine soy sauce, rice vinegar, minced garlic, minced ginger, agave nectar, and light brown sugar. Reserve 2 tablespoons and mix with cornstarch in a small bowl.

Add the fresh udon noodles to the skillet. Cover and steam for 2–3 minutes until heated through. Pour in half of the prepared sauce and stir gently.

Add your protein, remaining sauce, and cornstarch slurry. Stir vigorously for 3–4 minutes until the sauce thickens.

Remove from heat and plate the noodles. Garnish with cilantro, spring onions, and sesame seeds.