Start by placing the all-purpose flour and softened butter into a large mixing bowl. Mix until the mixture resembles coarse crumbs.

Add in the egg, granulated sugar, salt, and vanilla extract, and mix until the dough almost comes together.

Transfer the dough onto a lightly floured surface and knead gently until smooth, about 2 minutes.

Shape it into a disc, wrap it in plastic wrap, and refrigerate for 30 minutes.

Once chilled, roll the dough into a rectangle approximately 7x11 inches in size.

Gently spread the softened Nutella over the rolled-out dough, leaving a 1/2 inch border.

Starting from the long side, carefully roll the dough into a tight log and wrap in plastic wrap.

Refrigerate again for another 30 minutes.

Preheat your oven to 350°F (180°C) while the log is chilling.

Slice the log into 1/2 inch thick pieces and place on a parchment-lined baking sheet.

Bake for about 20 minutes, then cool on the baking sheet for 5 minutes before transferring to a wire rack.