Fillet steak with potato gratin

Mix the crushed garlic and oil together. Rub all over the fillet, cut into 4 portions, and set aside while you prepare the gratin.
Heat 30 ml of the butter in a frying pan, add the onions and cook until golden.
Layer half of the potatoes in a greased ovenproof dish, so that they overlap. Cover with half the onions and drizzle with 20 ml of butter.
Season with salt and freshly ground black pepper.
Cover with a layer of the sweet potatoes, the remaining onions and 20 ml butter.
Top with the remaining potatoes. Brush the remaining butter over the top of the potatoes. Season with salt.
Cover with foil and bake in a preheated 180 ºC oven for 40 minutes.
Remove the foil and bake for a further 20 minutes until golden.
While the potatoes are cooking, mix the soft butter with the sun-dried tomatoes and thyme.
Spoon onto a piece of foil or plastic wrap and roll up to form a thick sausage shape. Place in the freezer.
Just before potato gratin is ready, cook the meat. Heat a heavy-based pan over a high heat. When it is hot add the steaks and any leftover oil.
Continue to fry over a high heat until meat is well browned and cooked to taste.
To serve, remove the butter from the freezer. Cut into 4 slices and top each steak with a slice.
Serve immediately with the potato gratin and seasonal vegetables.