Preheat the oven to 357°. Put the barley, buckwheat groats, or farro* in a small saucepan and add 3 cups of water. Bring to a boil, stir, then reduce heat to a lightly bubbling simmer. Leave the pan uncovered, and cook the grains until plump and tender, stirring occasionally. This will take between 15-60 minutes depending on your grain of choice. Drain, and set aside.
Place the sliced Delicata squash rings on a small baking sheet, drizzle with one tablespoon olive oil, and sprinkle with salt and pepper. Place into the hot oven for 20-25 minutes until fork-tender and beginning to brown in some places, flipping halfway through.
About 5 minutes before the grains are finished cooking, warm one tablespoon olive oil in a large skillet over medium high heat until shimmering. Add the pancetta and garlic. Move the pancetta and garlic around in the skillet with a wooden spool or spatula until it is rendered, crispy, and slightly browned. Reduce the heat to medium and add the spinach. Toss the spinach in the warm pancetta garlic oil until it is just beginning to wilt, about 2-3 minutes. Add the warm cooked grain and sherry vinegar to the spinach, and toss until well coated in the vinaigrette.
Place the spinach and grains on a serving plate. Arrange the Delicata slices on top, sprinkle with hazelnuts, and place the egg on top. Serve.