Wash the lettuce leaves thoroughly and spin dry in a salad spinner or drain them thoroughly on a colander (otherwise you'll have a soupy salad).
Peel and slice the oranges: You need to remove the orange peel and the white pith. The easiest way to do it is to place the orange on a cutting board, cut off the orange peel along with the white pith with a downward, curved movement, using a sharp knife. Rotate the orange until it's completely peeled, then cut off the bottom. Cut the orange into slices (you can see it on photos in the body of the post).
Remove the seed from the pomegranate fruit: Using a pairing knife remove the top of the pomegranate. Score the sides along the ridge down toward the bottom of the pomegranate. Try not to cut the seeds. Peel the pomegranate, then cut it into parts between the segments (just the white part). You can also break the pomegranate into segments with your hand without peeling it first (it depends on the pomegranate which way is easier). De-seed the segments. Measure out 2/3 cup of the seeds.
Toast the walnuts: chop roughly the walnuts and place on a hot dry pan. Toast, stirring from time to time until the nuts are fragrant and browned. Take them off the pan immediately (they can easily burn).
Make the dressing: Add all the ingredients for the dressing into a medium jar, close the lid and shake with the jar intensively, until all ingredients are well combined. You can also mix the dressing in a food processor - then you won't need to chop the mint leaves. Make sure to mix it at the lowest speed possible (olive oil mixed at high speed can become slightly bitter).
Assemble the salad: Place the salad leaves on one big plate, top with the orange slices. Sprinkle with pomegranate seeds, walnuts, crumble feta cheese on top. Spoon the sauce over the salad, season it lightly with salt, pepper, and serve.