Line a 9x5 inch loaf pan with plastic wrap, pressing it into the corners and leaving enough overhang on the sides to lift the dessert out later. The pan should be fully covered up to the top so the chilled tiramisu releases cleanly instead of sticking.

Whip the heavy cream until it reaches soft peaks, then gently fold in the room temperature mascarpone and Nutella with a silicone spatula. Stop folding as soon as the mixture looks smooth and streak-free, because overworking it can turn the cream heavy or slightly curdled.

Stir the coffee and liqueur together in a bowl, then dip each ladyfinger very briefly before laying it into the bottom of the pan. A quick 1-second dip per side keeps the cookies tender and cake-like without letting them collapse.

Spread about 1/3 of the Nutella cream over the first cookie layer. Smooth it all the way into the corners so the finished slices hold even layers from edge to edge.

Add a second layer of dipped ladyfingers and lightly press them down with a spatula. Use a gentle touch here so the cookies settle into the cream without squeezing the filling out.

Repeat the cream and cookie layering once more, then finish with the last layer of Nutella cream across the top. The final surface should look level and fully covered, with no bare corners or exposed cookies.

Chill the tiramisu at least 6 hours or overnight, then lift it from the pan and slice, or cut it directly in the pan and serve cold. Once properly chilled, the layers should hold together neatly and feel creamy rather than loose.