Preheat the oven to 375 degrees F. Spray a 13 by 9-inch baking pan with nonstick cooking spray.
Place the biscuit pieces evenly in the bottom of the prepared pan. Sprinkle the crushed ginger thins evenly on top of the biscuits. Top evenly with the crystallized ginger.
In a large bowl, combine the half-and-half, eggs, brown sugar, molasses, vanilla, and butter. Pour over the biscuits layer and let stand until the liquid is absorbed, about 45 minute. Bake until fluffy and golden, 45 minutes to 1 hour. Serve warm with Molasses Butter Cream Sauce. Garnish with walnuts, if desired.
In a medium saucepan over low heat, combine the butter, cream, milk, and molasses. When at a low simmer, add the brown sugar and Irish cream liqueur. Slowly add the cornstarch mixture and cook until thickened. Stir in the walnuts.
In a small bowl, combine the cornstarch and water.
Day-old biscuits work best in this recipe. To easily crush ginger thins, place in a plastic resealable bag, seal, and crush with a rolling pan.