Roast Beef With Celeriac Mashed Potatoes - cooking recipe

Ingredients

1 (2 1/4 lb) beef tenderloin
2 medium bulb celeriac, trimmed, peeled, cubed
3 None medium potatoes, peeled, cubed
1 tsp lemon juice
1/2 cup milk, warmed
2 tbsp butter
3.5 oz small button mushrooms, halved
3.5 oz cremini mushrooms, sliced
1/2 cup red wine
1 2/3 cups beef stock
1 tsp whole grain mustard
2 tbsp fresh tarragon leaves

Preparation

Preheat oven to 350\u00b0F. Heat an ovenproof frying pan over high heat. Season beef then brown well on all sides. Transfer to oven and cook for 20-25 mins.
Meanwhile, place celeriac and potato in a large saucepan. Cover with water and add lemon juice. Bring to a boil. Cook for 15-20 mins, until tender. Drain then return to saucepan and heat over low heat for 1 min, until excess water evaporates. Mash with milk and 1 tbsp butter until smooth. Season to taste. Keep warm.
Remove beef from pan, cover loosely with foil and let rest for 5 mins.
Add remaining butter to frying pan and place over high heat. Cook mushrooms for 3 mins, until golden brown. Remove from pan.
Deglaze pan with wine, scraping up any browned bits. Simmer for 1 min then add stock and mustard. Reduce heat to medium and simmer for 5 mins, until reduced by 1/2. Return mushrooms to pan along with 1 tbsp tarragon. Simmer for 1 min.
Serve beef with celeriac mashed potatoes. Top with mushroom sauce and remaining tarragon.