In a large skillet, add the olive oil over medium-high heat. Add the onions and 1/4 teaspoon each of salt and pepper. Cook, stirring constantly, until the onions begin to soften, about 5 minutes.

Stir in the brown sugar and cook more, scraping the browned bits off the bottom of the pan frequently until the onions are golden brown, about 20 minutes. Remove the onions and place on a plate, set aside.

Preheat the oven to 375 degrees F.

To the same skillet you caramelized the onions in, add the chorizo and brown all over, about 5 minutes. Once the chorizo is browned, add the garlic, jalapeno and chipotle chilies, cook another minute or so. Stir in the chopped artichokes and spinach until combined. Remove from the heat and stir in the cilantro.

Add the cream cheese to skillet and stir until the mixture is combined. Stir in 1/3 of the fontina and all of the onions, reserving the rest of the fontina for topping.

Grease a baking sheet and remove the stems from the mushrooms. Spoon the mixture into each mushroom. Bake for 20 to 25 minutes or until hot and bubbly. Remove from the oven and garnish with chopped cilantro. Serve warm!