Preheat your oven to 350°F (175°C) and fit thawed frozen puff pastry in an 8 or 9-inch tart pan. Refrigerate while preparing filling.

In a large skillet, melt 2 tablespoons of unsalted butter over medium-high heat. Add thick-cut bacon slices and cook until crispy, about 5-7 minutes. Remove bacon and allow it to drain.

Sauté one diced onion in the leftover bacon fat for 3-4 minutes until translucent. Add thinly sliced potatoes and a pinch of fresh dill, seasoning with salt and pepper. Cook for an additional 3-5 minutes.

Remove the tart pan from the refrigerator and spoon the potato and onion mixture into the pastry crust. Drizzle heavy cream over the filling, leaving room for the crust to puff.

Bake on the lower rack of the oven for 35-45 minutes until the crust is golden brown and the potatoes are fork-tender.

Let the pie cool for about 10 minutes. Garnish with chopped chives or scallions before serving.