Preheat your oven to 350°F (175°C). Press thawed sheet of frozen puff pastry into an 8 or 9-inch tart pan, crimping edges.

Melt 2 tablespoons of butter in a skillet over medium-high heat. Add chopped thick-cut bacon, cooking until crispy and golden, about 5-7 minutes.

Reduce heat to medium, add sliced onions and cook for 2-3 minutes. Then add sliced potatoes and fresh dill, seasoning with salt and pepper. Stir gently for 3-5 minutes.

Spoon the potato mixture into the prepared pastry crust. Drizzle heavy cream generously over the filling.

Bake on the low rack for 35-45 minutes, or until crust is golden brown and filling is bubbling. Check for fork-tender potatoes.

Let the pie rest for 10 minutes. Garnish with freshly chopped chives or scallions before serving warm.