Thai beef salad

• 600 g (1 1/4 lb) rib-eye steak (2 x 300 g)
• 90 g (3 oz) Thai rice noodles

Marinade:

• 30 ml (2 tbsp) lemongrass, minced (optional)
• 15 ml (1 tbsp) ginger, chopped
• 15 ml (1 tbsp) garlic, chopped
• 60 ml (1/4 cup) soy sauce
• 60 ml (1/4 cup) lime juice, freshly squeezed
• 45 ml (3 tbsp) mixed light sesame and soybean oil 
• 30 ml (2 tbsp) sugar
• 15 ml (1 tbsp) nuoc mâm (fish sauce)
• 5 ml (1 tsp) sambal oelek (chili sauce)

Vinaigrette:

• 60 ml (1/4 cup) mixed light sesame and soybean oil
• 30 ml (2 tbsp) lime juice, freshly squeezed
• 30 ml (2 tbsp) soy sauce
• 15 ml (1 tbsp) nuoc mâm (fish sauce)
• 10 ml (2 tsp) sugar
• 1.25 ml (1/4 tsp) crushed chili pepper
• 1 mango, not too ripe, cut into strips  
• 1 red bell pepper, cut into strips  
• 125 ml (1/2 cup) grape tomatoes, cut in half
• 1/4 English cucumber, seeded and cut into half-moons  
• 30 ml (2 tbsp) green onion, sliced
• 30 ml (2 tbsp) fresh mint, chopped
• 30 ml (2 tbsp) fresh coriander, chopped
• 1 Boston lettuce
• 97 ml (7 tbsp) peanuts, unsalted, toasted and crushed