New York City — Steak n Shake Inc. is bringing to market 15 restaurants the company closed during the last 12 months. Keen-Summit Capital Partners LLC and NAI Global have been retained to run a sale process of the portfolio with a bid deadline of August 31 and auction date of September 4. It is anticipated additional properties will be sold by Keen-Summit Capital Partners through an auction during September. “Real estate investors and restaurants looking to expand their portfolio are in a position to take advantage of this opportunity, …