Add the mixed vegetables, garlic, ginger, tamari, vegetable broth, and sesame oil to the slow cooker. Stir gently to combine.
Cover and cook on low for 4 hours until the vegetables are tender but still hold their shape.
In the final 30 minutes, stir in the cubed tofu and continue cooking on low.
Mix the cornstarch with 2 tablespoons of water to form a slurry. Stir the slurry into the slow cooker and cook for 10 more minutes until the sauce thickens slightly.
Ladle the stew into bowls and top with sliced green onions and sesame seeds before serving.