Preheat the oven to 425 degrees F. Line 2 baking sheets with parchment paper. On a lightly floured surface, roll out the puff pastry into a 12-inch square, then cut into 4 equal squares. Slightly fold and pinch the edges of each square to form 4 round tart shells. Transfer to the prepared baking sheets and prick all over with a fork. Bake until golden, 8 to 10 minutes.

Meanwhile, cook the bacon in a medium skillet over medium heat, turning, until crisp, 8 to 10 minutes. Transfer to paper towels to drain, then crumble.

Let the tart shells cool slightly on the baking sheets. If the centers are very puffy, prick with a fork to deflate. Sprinkle evenly with the havarti and parmesan. Make a shallow well in the cheese in the center of each tart and crack an egg into each; season with salt and pepper. Top with the bacon, then return to the oven and bake until the egg whites are set, 10 to 15 minutes. Top with chives.

Photograph by Steve Giralt