Preheat oven to 325° F. Coat the cups of a 6-cup muffin pan with the softened butter; refrigerate pan.

Add salt to a large saucepan of water; bring to boil over medium-high heat. While waiting for water to boil, sauté onion in olive oil in a medium nonstick skillet until lightly browned and softened.

Transfer onion to a large mixing bowl and set aside.

Add matchstick potato pieces to the boiling, salted water and cook 3 - 4 minutes. Strain off the water and add potatoes to the bowl with the onions.

Cool potatoes and onions to room temperature.

To the cooled mixture, add olive oil, thyme, smoked salmon and black pepper to taste; mix thoroughly. 

Using clean hands, shape potato mixture into 6 equal portions; press each portion into a muffin cup of the pre-buttered pan.

Bake in preheated oven for 20 minutes, or until golden brown. Remove the muffins from the pan and top with a dollop of sour cream and a sprinkling of chives.