Myself and three of my personal chefs are contracted to do single-burner demos in Fresh Market grocery stores in two cities. The company that contracts us has a national account with Kroger also.
There a couple "rules of thumb" the demos are designed around.
First, don't bother demoing something your customers can't easily make at home. The goal of a demo is to promote and sell the products you are sampling. If the customer can't do the recipe themselves, or if the product looks complicated to use, you'll scare people away from it instead of driving them to it.
Second, provide a printed recipe, know the price of your main ingredients and where they are located in the store. If your demo is good, people will grab a recipe and go buy the ingredients.
Third, don't do anything that takes more than one pan. The demos we do can all be done in a 10 inch skillet.
Fourth, don't do recipes that take more than 5 minutes to cook. Preferably 3 minutes or less. You have a limited time frame. If you can't pump out samples to get the food into people's hands, you can't get them to grab the recipes and buy the ingredients. Also, people do want to watch you do the recipe IF it is a recipe they can do at home without a lot of hassle. If the recipe takes too long, they won't watch and likely won't buy.
Fifth, stock non-refrigerated ingredients near your demo station so you can direct people right to them. You'll sell more that way.
Sixth, don't be afraid to use bottled sauces. You are a grocery store, not a restaurant. You sell bottled sauces.
Seventh, don't sample anything you can't stick on a toothpick or put in a 1 oz plastic cup. You aren't there to feed people, you're there to sell them.
Eighth, it is completely OKAY to cook an prepped raw item from the seafood/meat/deli counter. Usually, they sell the best at demos because they require the least work. People just want to know what to do with them.
Ninth, don't bother making a whole meal. Just do a recipe for a main ingredient. People can buy a box of Mediterranean cous cous and some broccoli to serve as a side without you showing them how to cook them.
Tenth, personality sells food in the demo. If you don't smile and engage the people, they won't watch which means they won't buy.
Eleventh, get rid of the microwave. As soon as you put something in the microwave, you lose credibility to the customers. Sure, they microwave, but you're supposed to be a chef.
Twelfth, don't demo cheap products. You are there to sell food. The cheap stuff sells itself. Yes, the expensive stuff is an investment, but once you get a recipe in someone's hand and teach them how to make it, they'll return many times for the product. Just make sure your sample sizes are only one bite.
As to what you should make? Start with the question, "What does the store want to sell?". You can sell anything in a demo with a nice, simple, delicious recipe. If they have prepared crab cakes in the seafood counter, sauté them in some olive oil, cut them into bite size pieces and serve them in a 1 oz plastic cup with a dab of a prepared sauce you sell. Stock the sauce at the demo table. Cook some of the marinated chicken tenders you have in the meat case. Serve them on a piece of a taco-size flour tortilla cut into eight pie shaped sections, on top of a little lettuce chiffonade with a salsa you guys sell. We did a lamb leg slice seared, then cut into bite size pieces and tossed in red wine and bleu cheese sauce similar to the dish you mentioned. You could do the same thing with a thin steak. The meat cut size doesn't have to be the same size as how you sell it. You could also do mussels really easy in a 10 inch skillet. Toss them in some white wine, fish/chicken stock and lemon juice, tossing some butter in when they are done. You'll need something to cover the pan while they cook. You can sell your spice rubs by rubbing steaks or porkloin chops and pan seared them. Cut into bite size pieces and stick with a toothpick. Shrimp are always easy. Saute them and toss them in a bottled curry sauce you sell.