Position an oven rack in the middle of the oven. Preheat the oven to 350 degrees F.
Spray a 7 by 10 3/4-inch nonstick baking pan with vegetable cooking spray. Lay a 6 by 18-inch piece of parchment paper in the pan, allowing the excess paper to overhang the sides. Spray the parchment paper lightly with cooking spray.
In a medium bowl, combine the cookie dough, 1/2 of the chopped chocolate-toffee candy pieces and vanilla extract. Using damp fingers, gently press the dough into the prepared pan. Using the tines of a fork, prick the dough all over. Bake for 12 to 14 minutes until the crust is lightly browned. Cool for 15 minutes.
Place the chocolate chips and vegetable oil in a medium bowl. Place the bowl over a pan of simmering water and stir until the chocolate has melted. Cool the chocolate mixture for 10 minutes. Whisk in the mascarpone cheese until the mixture is smooth. Using a spatula, spread the chocolate mixture over the cooled crust. Sprinkle the remaining chocolate-toffee candy pieces and sliced almonds over the chocolate mixture. Refrigerate for at least 2 hours until the chocolate layer is firm.
Peel off the parchment paper and cut into 1 1/2 by 2-inch bars. Serve at room temperature.
*Cook's Note: To toast almonds, arrange in a single layer on a baking sheet. Bake in a preheated 350 degrees F oven for 8 to 10 minutes until lightly browned.