Peel, core, and thinly slice the pears, then toss them in a bowl with the lemon juice. This keeps them from browning while you prepare the other components. Set aside.

In a large mixing bowl, beat the mascarpone cheese with a hand mixer on medium speed for about one minute until smooth and creamy. Add the cold heavy cream, powdered sugar, and vanilla extract. Continue beating on medium-high speed until stiff peaks form, about two to three minutes. The cream should hold its shape firmly when you lift the beater. Do not over-beat or it will become grainy.

Arrange about half of the gingerbread cubes in a single layer across the bottom of a large trifle dish or glass bowl. Press them in gently so they fit snugly but are not crushed.

Spoon about half of the mascarpone cream over the gingerbread layer and spread it to the edges using a spatula or the back of a spoon. Arrange about half of the sliced pears over the cream in a fairly even layer.

Repeat the layers in the same order: remaining gingerbread cubes, the rest of the mascarpone cream, and then the remaining pear slices arranged attractively on top.

Dust the top evenly with ground cinnamon. If using, scatter the crushed ginger snap cookies over the surface for a little crunch and a finished look.

Cover the trifle tightly with plastic wrap and refrigerate for at least three to four hours before serving. This rest time allows the gingerbread to absorb some of the cream and the flavors to come together. Serve cold, scooping down through all the layers into each bowl.