Saus Bawang Perancis buatan sendiri

Bahan-bahan (2 porsi)

• 3 tbsp butter
• 2 1/2 cups diced onions ((2 to 3 onions) (brown, yellow or white))
• 3/4 tsp salt
• 1/2 tsp black pepper
• 1/2 tsp onion powder
• 1/4 tsp cayenne pepper
• 4 oz / 120 g cream cheese ((cold), cut into cubes)
• 1/4 cup whole egg mayonnaise
• 1/2 cup sour cream ((full fat is best, but you can use low fat or even yoghurt))