Over medium low heat, melt the olive oil and one tablespoon butter. Add leeks and salt and stir. Cook stirring occasionally until leeks are tender, about 8 minutes. Add a dash of cranberry pear white balsamic and sauté a minute more until most of the vinegar has evaporated.

Add spice rub and cream. Simmer uncovered until thickened or about 10 minutes. Transfer to bowl and cool.

Peel and slice potatoes evenly into approximately 1/8 inch slices. Dump slices in cold water as you slice so that the potatoes don't turn brown.

Grease a gratin dish with remaining butter and preheat oven to 300 degrees

Once you are ready to assemble, drain the potatoes being careful not to break them. Layer 1/4 of potatoes, 1/3 of leek mixture, 1/3 cheese and a sprinkle of salt and pepper. Repeat 2 more times. The last layer should be just a layer of potatoes.

Finish with a few shavings of gruyere. Bake for approximately 1 ½ hours. Do not let cream boil to avoid it separating and curdling. It's done when it has a nice golden brown to orange color; the potatoes are tender but still hold their shape; and the cream has thickened and reduced slightly. Let cool for 15 to 20 minutes before serving.