Wellington Lamb - Icelandic Lamb

Ingredients

• 250 g mushrooms
• 3 shallots
• 4 cloves garlic
• 5 tbsp. fresh thyme
• 2 tbsp. olive oil
• salt and ground black pepper
• 4 lamb fillets
• 1 tbsp. oil
• 1 tbsp. butter
• 2 sheets puff pastry
• 1 egg yolk
• Kosher salt
• 50 g butter
• 50 g flour
• 2 ½ dl (1 cup) lamb stock
• 1 dl (3.5 fl. oz.) heavy cream
• 1 tsp black pepper
• 1 tsp thyme
• 3 tbsp. honey
• 3 tbsp. balsamic vinegar
• 100 g hazelnuts
• mixed green salad, such as ruccola or spinach
• 1 tbsp. whole grain mustard
• 4 medium size potatoes
• 1 tbsp. olive oil
• salt ground black pepper
• 2 tbsp. crème fraîche
• 3 tbsp. grated Parmesan
• 1 tbsp. chopped parsley