-
1
Preheat the oven to 180C (350F/Gas 4).
-
2
Peel the potatoes and slice in half down the middle.
-
3
Trim the rounded side then cut out a ring of potato from each half using a 6cm (21/2 in) round cutter so that you have a cylinder of potato.
-
4
Lay the butter slices in the bottom of an ovenproof saute pan.
-
5
Put the potatoes on top and add water to almost cover the potatoes.
-
6
Bring to the boil, turn the heat down, and simmer gently for 30 minutes until the potatoes are just tender.
-
7
Turn the potatoes, add the thyme and garlic, and cook for another 20 minutes.
-
8
Drain the potatoes and keep warm.
-
9
For the sauce, pour the stock into a pan, boil to reduce by two-thirds, then whisk in the cream.
-
10
Fry the mushrooms in butter for 5 minutes until golden brown, then add to the stock and cream.
-
11
Season to taste.
-
12
Reheat gently before serving.
-
13
Rub the beef all over with the olive oil and season generously.
-
14
Heat a large ovenproof frying pan until smoking, then add the beef and sear for 2 minutes on each side until golden brown.
-
15
Transfer to the oven and roast for 15-20 minutes until cooked to your liking, then remove from the oven and rest for 15 minutes.
-
16
Meanwhile, make the onion puree.
-
17
Heat the butter and oil in a pan.
-
18
Add the onion, garlic, and thyme.
-
19
Cook gently for 15 minutes until completely soft but not brown.
-
20
Cool slightly.
-
21
Puree in a blender until smooth.
-
22
Return to the pan and season.
-
23
Reheat gently before serving.
-
24
To serve, spread a little onion puree on each plate, Carve the beef into 4 thick slices and place on top of the puree.
-
25
Serve with the fondant potatoes and the mushroom sauce.
