Preheat the oven to 400?F.
Set a medium skillet over medium-high heat and add a drizzle of oil along with the butter. (If you have a small-ish cast iron skillet, that's perfect - it can slide right into the oven, and will hold the heat well and keep the dip warm longer). Sauté the onion for 4-5 minutes, until soft and starting to caramelize. Add the artichokes and cook for a few minutes to heat through and get rid of any excess moisture.
Stir in the mayo, cream and almost all the Jarlsberg, leaving about half a cup to sprinkle on top. Season with salt and pepper and stir to combine everything well. If your skillet isn't ovenproof, scrape the mixture into a shallow baking dish. Sprinkle with the rest of the Jarlsberg.
Bake for 10-15 minutes, until the cheese is bubbly and golden around the edges. Serve immediately, with crackers or crusty bread for dipping.
Serves 6 (or 1).