Best butter substitute for a particular baking recipe?

There’s a brownie recipe I want to make for family this Thanksgiving, one of whom is allergic to milk. I figured I could just look up a butter substitute and use that.

However, this particular brownie recipe promises a chewy texture, and the best way to get it, the magazine says, is to use a particular combination of saturated and unsaturated fat, with butter taking the saturated role and adding flavor.

So which butter substitute is best for that particular purpose?

There are butter flavored and colored shortenings available. Crisco makes one in both stick and tub packages. I’ve used it in the past with success.