Apple and Root Vegetable Hash

I love Fall vegetables and this is a great way to serve them.

Apple and Root Vegetable Hash

Coarse salt and freshly ground pepper
3/4 pound celery root, peeled and cut into 1/2 inch pieces (2 cups)
3/4  pound Yukon Gold potatoes, peeled and cut into 1/2 inch pieces ( 2 cups)
3/4 pound sweet potatoes, peeled and cut into 1/2 inch pieces (2 cups)
1/4 cup extra virgin olive oil, divided
1 onion, diced
2 small firm, sweet apples, peeled and cut into 1/2 inch pieces (2 1/2 cups)
1/4 cup roughly chopped fresh sage leaves

1. Bring a medium pot of water to a boil, and generously season with salt.  Add celery root, and simmer 3 minutes.  Add potatoes and sweet potatoes, and simmer vegetables 2 minutes more.  Drain well, and spread vegetables on a rimmed baking sheet.  Let cool 15 minutes.

2. Heat a 2 tablespoons oil in a large (preferably cast-iron) skillet over medium -high heat and cook onions until translucent and just beginning to color, about 2 minutes.  Add remaining 2 tablespoons oil, the apples, and vegetables; season with salt and pepper.  Stir to combine, then press into a single layer using a spatula.  Cook, undisturbed, 2 minutes.  Stir, and repeat process until vegetables are very tender and beginning to carmelize, 8 to 10 minutes more.  Remove from heat, Stir in sage, and season with salt and pepper.