Since there is more than one flavor of Twix besides the original caramel, I'd suggest trying to recreate some of the alternates (I know I'm going to.) There have been five kinds of Twix total. (That I'm aware of/in the U.S.A. I'm not sure about other countries.) The alternates are: Peanut Butter, Cookies and Cream, and Fudge. The Peanut Butter came first. Several years later, the other two were released simultaneously. All three were discontinued years later.

The Shortbread: Add some coaco powder to the dry mix for a chocolate Cookie.

Peanut Butter Twix: The first version had a normal shortbread cookie like the original caramel Twix. When it was brought back after the great Twix apocolypse, the plain cookie had been replaced with a chocolate cookie. To make this, sub out the caramel for a peanut butter mix. (Probably use the filling recipe from a reese's clone.) Choose whichever cookie you think is best. (Of course, you can do that on any cookie.)

Cookies and Cream Twix: Use a chocolate cookie and sub out the caramel for something resembling oreo cream. Again, use the filling recipe for any oreo cookie clone on the net. This was probably my favorite Twix at the time, but is something I'd not like as well now. (It Joins A&W Cream Soda on the list of things I LOVED as a kid, but (would probably) find WAY too sweet no.

Fudge Twix: Chocolate cookie. For the caramel, substitute a layer of fudge candy.