Grilled Lamb Sirloin with Herb Butter - Icelandic Lamb

Ingredients

• 2 200 gr sirloin steak, butterflied
• 2 tbsp. fresh lemon juice
• 2 tsp. finely grated lemon zest
• 1 1/2 tsp. chopped rosemary
• 1 garlic clove, chopped
• Freshly ground pepper
• 1/4 cup plus 1 tablespoon olive oil
• 80 g butter, soft
• 2 tbsp. parsley, chopped
• 2 tbsp. tarragon, chopped
• 2 tbsp. chives, chopped
• 2 tsp. Dijon mustard
• 2 tsp. wholegrain mustard
• 2 cups finely sliced red cabbage
• 1 small fennel bulb, sliced
• 1/2 green apple, cored, quartered and sliced
• 1 tbsp. grated horseradish
• 2 tbsp. rapeseed oil
• 1 tbsp. apple cider vinegar