Defrost the spinach and squeeze every bit of water out that you can, making sure it is as dry as possible. Heat a skillet over medium and sauté the garlic in the butter for about 20 seconds, careful not to burn it.
Add in the heavy cream, mascarpone, cream cheese, salt and pepper and mix until the cheese has melted. Then add in the grated asiago. Add in the spinach and simmer (uncovered) on low for 5 minutes, or until thickened to your liking.
Allow to cool slightly before serving with a grating of asiago cheese over the top. Store leftovers in the fridge for a few days or freeze.
I used equal parts mascarpone and cream cheese. If you don't mind the extra carbs and want a tangier flavor, you can use all cream cheese instead.This is not a "soupy" version of creamed spinach, so if you prefer it that way, add a little more heavy cream. Be sure to add a little more salt as well.I use asiago cheese, but you can substitute with parmesan or Romano cheese if that's what you have on hand.