Bring a medium pot of water to a boil and salt it generously. Add the barley, reduce to a simmer, and cook until tender (about 10 minutes). Drain and toss with a drizzle of olive oil. Set aside to cool.
Meanwhile, set up a steamer basket over simmering water. Cut the potatoes into bite-sized pieces and steam until tender, about 10-15 minutes. Sprinkle with a little rice vinegar and salt, and gently stir to combine. Set aside to cool.
In the same steamer basket, steam the asparagus until tender, 3-8 minutes depending on thickness. Transfer to a cutting board, let cool slightly, and cut into bite-sized lengths. Set aside to cool. In the same steamer basket, steam the eggs for 12 minutes. Run under cold water to stop the cooking. Finally, yet again, in the same steamer basket, steam the chard leaves until tender, just 2-3 minutes. Toss with salt, olive oil, and cider vinegar, and set aside to cool.
Make the dressing: in a jam jar with a tight-fitting lid, combine the lemon juice and then pour in about twice as much olive oil as lemon juice (you can eyeball it). Then add the mustard, salt, pepper, and any minced herbs you have around (optional). Screw on the lid and shake well. If you like an extra dressing-y salad, you may wish to make a double batch.
Assemble your lunch containers. It helps to set 4 containers out on the counter. Then just divide all the ingredients evenly among the containers – barley, potatoes, asparagus, chard, and chickpeas. I suggest storing the eggs (in their shells) separately and peeling/slicing right before lunch, simply because I think they stay fresher this way. I would also suggest storing the dressing in a small container and dressing the salad right before eating, although everything here is hardy enough that it won’t wilt if dressed early.
Recipe Notes
The “rainbow” in the rainbow chard will dye the potatoes a bit pink. I liked this, but if you don’t, you might want to choose a non-rainbow variety.