Steak Sandwiches with Twice Baked Potato Bites

This manly take on steak and potatoes will have everyone asking for seconds!
the goods:

sandwiches:

1 boneless rib-eye steak, excess fat removed

1 large red onion

sliced2 hoagie rolls split

5 ounces cream cheese, room temperature

4 tablespoons grainy mustard

1 bunch baby spinach, stems removed

steak sauce for serving

potato bites:

10 to 14 red new potatoes (small), halved

1 tablespoon olive oil

3/4 cup sour cream

1/4 cup snipped fresh chives, plus more for garnish
Preheat oven to 450 degrees. Cut a thin slice off the bottom of each potato half so they rest flat.

On a rimmed baking sheet, toss with olive oil; season with salt and pepper, and arrange bottom side down.

Bake until tender, 30 to 35 minutes. Let cool on sheet.

When cool enough, using a melon baller, scoop out about a teaspoon from the center of each potato and place in a bowl.

Add sour cream and chives to the bowl with potato centers and mash; season with salt and pepper.

Stuff potatoes with filling.

Bake potatoes at 450 until lightly browned, about 15 minutes.

Meanwhile, saute onions in a pan with butter, until soft and browned, about 7 minutes.

Heat grill to high; lightly oil grates. Season steak with salt and pepper. Grill 5 minutes on each side for medium-rare. Transfer to a plate and tent with foil, let rest for 10 minutes.

Spread rolls with mustard on bottom side and cream cheese on top side.

Thinly slice steaks against the grain.

Place a layer of spinach on each roll.

Finished with a layer of onions.

Close sandwiches. Slice in half.

Remove potatoes from the oven.

Serve sandwiches with a side of steak sauce for dipping and twice baked potato bites.