Nibblous | beef fillet with sesame & ginger dipping sauce

Ingredients

• 600g beef fillet (or other good steak, I guess)
• 3 garlic cloves, finely chopped
• 2 teaspoons of sugar (approx - 'to taste')
• 6 tablespoons of light soy sauce
• 2 teaspoons of sesame oil
• 2 tablespoons of rice vinegar
• 2 spring onions, finely chopped
• 1 teaspoon peeled and finely grated ginger
• 2 tablespons of sesame seeds, toasted and crushed
• half a teaspoon of freshly ground black pepper
• 1 tablespoon of vegetable oil
• 1 red onion, sliced, for garnish