Beef stroganoff

Name: Beef stroganoff
Prep time: 10 min
Cook time: 35 min
Total time: 45 min
Cuisine: European, Eastern European
Ingredients: 1 tbsp olive oil; 1 onion sliced; 1 clove of garlic; 1 tbsp butter; 250g/9oz mushrooms sliced; 1 tbsp plain flour; 500g/1lb 2oz fillet steak sliced; 150g/5oz crème fraîche; 1 tsp English mustard; 100ml/3½fl oz beef stock; ½ small pack of parsley chopped