Preheat your oven to 400°F (200°C).

Roll out the thawed puff pastry sheet on a lightly floured surface until it forms a rectangular shape.

Transfer the rolled-out pastry onto a baking sheet lined with parchment paper.

Trim the bottoms of the endives and remove any damaged outer leaves. Cut each endive in half lengthwise.

In a large skillet, melt the butter over medium heat. Add the sugar and stir until it dissolves.

Place the endive halves in the skillet, cut side down. Cook for about 5 minutes, until the cut side is caramelized and golden brown.

Flip the endive halves and cook for an additional 3 minutes. Season with salt and black pepper.

Arrange the caramelized endive halves evenly on top of the puff pastry, cut side down.

Sprinkle the crumbled blue cheese over the endives.

In a small bowl, whisk together the eggs and heavy cream. Pour the mixture evenly over the tart.

Bake in the preheated oven for approximately 20-25 minutes, or until the puff pastry is golden brown and the filling is set.

Remove from the oven and let it cool slightly before serving.