Lightly spray a 9x13 high sided cake pan then line with parchment paper so it overhangs on the longer sides. Lightly spray the parchment as well.
In a large bowl combine the graham cracker crumbs and almonds.
Add the butter to a small sauce pot and melt over low heat. Once melted, whisk in the cocoa powder, sugar, egg and vanilla. Cook on low, whisking often, for 2-3 minutes or until thickened. If it starts to separate don’t worry, it’ll come back together when you mix it with the crumbs and almonds.
Pour over crumb mixture and stir together. Pour in the Kahlùa, mix then press into bottom of the prepared pan and freeze, about 30 minutes.
In stand mixer fitted with a whisk attachment or with a hand mixer, beat on medium the powdered sugar, butter, Kahlùa and cream until smooth and fluffy. Evenly spread over the crust. Place back in the freezer and freeze until firm, at least 30 minutes.
In a small sauce pot melt the chocolate and butter over low heat, about 2-3 minutes. Spread over the icing then sprinkle with the almonds and salt if using. Loosen up the sides that are touching the pan with a butter knife and carefully lift the bars out, using the parchment paper as handles. Cut into 2x3 inch bars and keep frozen until needed.