Slow cooker Mongolian Beef

Ingredients

• 2 lbs thinly sliced sirloin beef
• 1/4 cup cornstarch
• 2 medium onions (sliced)
• 1- inch fresh ginger (peeled and grated)
• 3 to 4 garlic cloves (peeled and pressed)
• 1 cup brown sugar
• 1 cup soy sauce
• 1 cup water
• 2 green onions (sliced diagonally (optional))
• Sesame seeds (optional)