Substitute fillet with sirloin, rump or ribeye steaks.
Pre-heat the oven to 200°C/390°F and line a baking tray with tinfoil.
Coat the bone marrow in olive oil, generously season with salt and pepper and arrange the bones on the baking tray cut side up.
Roast the marrow bones for 15 minutes or until the marrow starts to bubble around the edges. Set aside, allow to cool and push out the marrow into a bowl.
To make the bone marrow butter, add the butter to the bowl of marrow, stir in the fresh herbs and season to taste with salt and freshly ground black pepper. Keep this butter at room temperature for serving.
Coat the fillet steaks in olive oil and generously season with salt and freshly ground black pepper.
Add a splash of olive oil, 2 tablespoons of butter, thyme sprigs and garlic cloves to a smoking hot frying pan and cook the steaks for approximately 4 minutes on both sides for medium-rare.
To evenly brown all sides of the fillet, continuously spoon the hot butter from the pan over the steaks whilst cooking; this French technique is called arroser which means ‘to baste’.
Leave the meat to rest for half its cooking time, then spoon the delectable bone marrow butter over the top of the fillet medallions and serve.