Which ingredient is included in the Bechamel Steak Sandwich?

The Bechamel Steak Sandwich traditionally includes a rich, creamy sauce known as béchamel, which is made from butter, flour, and milk. The choice of ingredient that complements the béchamel sauce and enhances the overall flavor profile of the sandwich is roasted jalapeno. The heat from the roasted jalapeno creates a delightful contrast with the creaminess of the béchamel, adding depth and a touch of spice that elevates the sandwich.

In the context of the other ingredients, feta cheese, avocado, and basil aioli do not have the same traditional connection to this particular sandwich. Feta cheese may be used in other dishes for its tangy flavor, avocado provides a creamy texture but doesn't complement the béchamel in the same way, and basil aioli is a different sauce altogether that contributes a herbal flavor, which diverges from the classic pairing. Therefore, roasted jalapeno is the most fitting choice for enhancing the signature characteristics of the Bechamel Steak Sandwich.