A plateful of mixed greens would never be enough to satisfy me, no matter how delicious the vinaigrette. For me to "eat my greens", I need to add bulk in the form of protein and/or starch. This salad is light enough to enjoy when it's hot outside but substantial enough that they won't leave you feeling hungry within the hour.
Sprinkle fine sea salt lightly but evenly over the entire steak and leave at room temperature for about an hour (or wrap it in cling-film and refrigerate for several hours up to overnight; remove it from the fridge about 30 minutes before it's time to cook it).
Preheat the oven to 220° C (430° F). Cut the cherry tomatoes in half and drizzle with about 15ml (1 tbsp) of extra-virgin olive oil. Put the tomatoes cut-side up on a baking tray then sprinkle them lightly with salt. Bake for 10-15 minutes, or until they are lightly charred in spots. Meanwhile bring a pan of salted water to the boil, add French beans and cook for 3 minutes. Drain and place in a bowl of iced water.
Thinly slice the garlic and put it in a small pan with about 45ml (3 tbsp) of olive oil, or enough so that the slices are "swimming". Heat the oil until it starts to sizzle then lower the flame and cook until the garlic is golden brown. Watch carefully towards the end, to make sure the garlic doesn't get too dark. Drain the garlic slices on paper towels and reserve the oil. You can use this garlic oil in the vinaigrette.
To make the vinaigrette, put the mustard and a pinch of sugar in a bowl and start whisking in the olive oil a few drops at a time. Once a stable emulsion has been established, start adding the oil in a very thin stream, whisking constantly. Add the rice wine vinegar then season to taste with salt and pepper.
Use paper towels to dry the surface of the steak then rub about 20ml (4 tsp) of extra-virgin olive oil over the meat to coat it lightly but evenly. Heat a grill pan (preferably cast iron) over a medium-high flame until it's very hot. Cook the steak, flipping it over once, until done to medium-rare (about eight minutes in total, depending on the thickness). Put the steak on a cutting board and leave it to rest for about 10 minutes. Thinly slice it against the grain.
Tear the radicchio into bite-size pieces and separate the endive into individual leaves. Put the radicchio, endive, beans and greens in a bowl and mix in just enough vinaigrette to coat them lightly. Add the juices that have run out of the steak to the bowl and mix again, then sprinkle with freshly ground black pepper.
Arrange the salad on two plates. Add the sliced steak, cherry tomatoes and two anchovy fillets (if using) to each portion. Scatter the fried garlic on top and sprinkle lightly with rough-flaked sea salt. Serve immediately.