Place mascarpone, pumpkin puree, vanilla, cinnamon, nutmeg, and salt in a bowl and whisk until smooth and combined.
Using a stand mixer fitted with a whisk attachment, or a handheld mixer, whip heavy cream and powdered sugar until stiff peaks form. Gently fold the whipped cream into the pumpkin mixture until just combined. Transfer to a piping bag with an extra large round tip.
To assemble a tiramisu cup, pipe a layer of pumpkin cream into the bottom of a 12-oz stemless wine glass or jar. Dip a ladyfinger into espresso, break in half, and layer on top of the cream. Spread with 1 tablespoon of Challenge Chocolate Snack Spread and pipe a swirl of pumpkin cream on top. Repeat another layer of dipped ladyfinger, Chocolate snack spread and pumpkin cream.
Assemble 5 more tiramisu cups, cover, and chill for at least 3 hours. Dust with cocoa powder before serving.