For the croutons, preheat the grill to hot. Cut the crusts off the bread and discard. Cut the bread into even-sized small cubes. Sit a plastic bag in a bowl, pour in the oil and season with salt and pepper.
Add the cubed croutons to the bag, pick up the bag and shake, tossing the cubes in the seasoned oil. Tip the bread out on a baking tray and place under the grill. Turn until they’re evenly browned - watch them all the time to prevent scorching and shake occasionally to make sure they brown evenly.
For the salad, cook the broad beans in boiling water for about 3-4 minutes, or until tender. Drain and refresh in cold water. Remove the beans from their pods, set aside.
Trim the very ends off of the Little Gem lettuces but keep the root intact. Slice each lettuce into six wedges. Arrange on a platter, scatter with beans and parmesan and season with salt and pepper.
For the mustard dressing, measure all of the dressing ingredients into a clean jam jar, season with salt and pepper and seal with a lid and shake until combined. Pour over the dressing, toss and serve.