Beat egg yolks, sugar, and salt with a stand mixer fitted with a whisk attachment on high until pale yellow and doubled in volume, 4 to 5 minutes; scrape down sides and bottom of bowl.

Add mascarpone cheese and vanilla bean paste; beat on medium until creamy, about 1 minute. Transfer mixture to a large bowl; set aside.

Without wiping mixer bowl clean, add cream; beat on medium with whisk attachment until medium-stiff peaks form, about 2 minutes.

Spoon half of whipped cream (about 1 cup) into bowl with egg mixture, and gently fold until fluffy and combined. Reserve remaining whipped cream for layering; set aside separately.

Stir together espresso and bourbon in a medium shallow bowl.

Working with 1 ladyfinger at a time, dip each ladyfinger into espresso mixture for about 1 to 2 seconds; place dipped ladyfinger, rounded side up, in bottom of a 3- to 4-quart trifle dish or a 2-quart 8- x 8-inch baking dish.

Repeat dipping procedure using just under half (about 9) of the ladyfingers until an even layer forms, breaking ladyfingers in half as needed to fill in any gaps.

Roughly crumble 7 of the vanilla wafers over ladyfingers.

Spoon half (about 2 ½ cups) of mascarpone mixture over cookies, and spread in an even layer.

Top with remaining 1 cup whipped cream, and spread into an even layer.

Slice 2 bananas, and place in an even layer over whipped cream.

Repeat layering process with remaining espresso-dipped ladyfingers, 7 more crumbled vanilla wafers, and remaining half mascarpone mixture.

Cover using plastic wrap, and refrigerate for at least 4 hours or up to 12 hours.

When ready to serve, slice remaining 1 banana, and place in an even layer over top of mascarpone mixture.

Roughly crumble 3 vanilla wafers over top, and sprinkle with chocolate shavings as desired.

Garnish with remaining 5 whole vanilla wafers, poking into top of tiramisu as desired.