Start by seasoning the beef with salt and pepper and rub in the olive oil. Heat a pan till flaming and seal the meat on both sides, adding the sprigs of thyme or rosemary into the pan whilst cooking. Transfer to an oven dish and continue to cook in the oven for 15-20 minutes or to your liking. Meanwhile, add the garlic and shallot to the same pan, along with the butter and saute till soft for 4-5 minutes. Add in the sliced Portobello mushrooms, season with salt and pepper and cook for a few minutes. Splash in the wine to evaporate, pour in a little cream and cook for 2-3 minutes. Next, mix together the pesto and 2 tbsp extra virgin olive oil. Mix together and use as a dressing for the rocket and cherry tomato salad. To serve, thickly slice the cooked and rested beef tagliata and place onto a serving board. Spoon over the creamy Portobello mushrooms and top with the pesto rocket salad. Finish off with Parmesan shavings and serve immediately.