Place 1 pound of clear melt and pour soap in a microwave-safe measuring cup. Microwave in 30 second increments, stirring between until completely melted.

Add Guinness scented oil and shea butter to a second microwave-safe measuring cup. Microwave in 30 second increments, stirring between until completely melted.

Add to melted soap base with dark brown color and mix well. 

Spray the mold with rubbing alcohol.

Immediately pour the soap mixture into the mold and spray with rubbing alcohol. Allow the soap mixture to harden at least 2 hours or until completely firm. 

Place remaining 1/2 pound of clear melt and pour soap in another measuring cup. Microwave in 30 second increments, stirring between each until completely melted.

Add Guinness scented oil and golden color. Mix well. 

Spray the top of the hardened brown soap with rubbing alcohol.  This will allow the two layers to adhere to each other.

Add the golden soap mixture into the mold. Spray the top of the golden soap mixture with rubbing alcohol. Allow this layer to harden for at least an hour.  

Place whipped soap base and glycerin in a second mixing bowl and whip for 1 minute. 

Fold in the cornstarch into the soap.

Add the melted clear soap base and mix for 1 minute.

Add 1 drop of the dark brown soap color and beat continuously until the mixture forms peaks, like a meringue.  If you'd liked to make your frosting stiffer, add more cornstarch and beat.

Place frosting in your piping bag.

Spray the top layer of soap with rubbing alcohol and pipe frosting on top. Work quickly because the frosting will start to harden in about 5 minutes. 

Allow your Guinness soap to harden for about 2-3 days before cutting.

Enjoy!