Preheat oven to 400 F.

To make Hasselback potatoes: Using vegetable brush, wash potatoes. Dry well and place on cutting board. Arrange handles of two wooden spoons so they are alongside potatoes to prevent knife from slicing all the way through. Make several cuts down each potato about 1/4 inch apart. Repeat with remaining potatoes and arrange on baking sheet fitted with wire rack.

Drizzle with olive oil, making sure some oil is in slices. Sprinkle salt on each potato.

Bake 90 minutes, or until potatoes are crispy on outside, fluffy in center and internal temperature is 205 F. Remove from oven and allow to cool slightly.

To make caramelized onions: In heavy-bottomed shallow pan over medium heat, melt butter. Add sliced onions and season with salt. Continue to cook, stirring regularly until onions are deep brown and caramelized. Deglaze pan with cognac or brandy, if desired, scraping caramelized bits off bottom of pan. Remove from heat and set aside.

To assemble, sprinkle potatoes with cheese, about 1/4 cup per spud, ensuring some cheese is in potato slices. Place cooked bacon pieces in some slices.

Return potatoes to oven for about 5 minutes, just long enough to heat potatoes slightly and melt cheese. Place potatoes on serving platter and garnish with caramelized onions, sour cream and chopped chives.