Preheat your oven to 350°F (175°C). Press thawed puff pastry into an 8 or 9-inch tart pan and chill in the refrigerator.

In a skillet, melt 2 tablespoons of butter over medium-high heat. Add diced bacon and cook until crispy, about 5-7 minutes. Stir in onions and cook until softened, then add potatoes and dill.

Remove the chilled crust and fill with the creamy mixture. Drizzle heavy cream over the top.

Bake on a low rack for 35-45 minutes until golden brown and filling is bubbling.

Let cool for about 10 minutes, garnish with chives or scallions, slice, and serve.