Line a 9x13-inch pan with cinnamon graham crackers.
In medium saucepan, combine the melted butter, sugar, egg and milk. Cook over medium-high heat, whisking constantly, until it reaches custard consistency (thickened). Remove from heat and cool. Add the crumbs, pecans and toffee bits. Spread the mixture over the graham crackers. Top with another layer of cinnamon graham crackers.
Combine the frosting ingredients, and frost the top of the graham crackers. Sprinkle with chopped pecans.
Cover and refrigerate overnight. Cut into small squares or bite-sized pieces.