Place the eggs in a medium saucepan and cover with cold water by one inch.
Bring the water to a rolling boil, then immediately turn off the heat, cover the pan, and let the eggs sit for 9 minutes.
Prepare an ice bath in a medium bowl while the eggs cook.
Transfer the eggs to the ice bath for 5 minutes, then gently crack the shells and peel them under cool running water.
Finely dice the peeled eggs and the celery, and thinly slice the green onions.
In a clean mixing bowl, whisk together the nonfat Greek yogurt, Dijon mustard, sea salt, black pepper, and smoked paprika until the dressing is smooth.
Gently fold the chopped eggs, celery, and green onions into the yogurt dressing until every piece is well coated.
Toast the sprouted grain bread slices until they are golden brown and crisp.
Place the fresh arugula on one slice of toast, scoop the egg salad over the greens, and top with the second slice of bread before serving.