Heat oil in a large saucepan over medium heat.
Add onions and saute until soft and translucent, about 5 minutes.
Add spinach, cream cheese and cream, stir to incorporate. Simmer until the cream cheese has melted and the dip has reduced slightly, about 8 to 10 minutes.
This yummy dip can be made a day in advance, store in the fridge in an airtight container. Warm before serving.
If you're making the dip the day of and you want to get slightly ahead, stop after the stirring in the spinach, cream cheese and 1 cup of cream and set aside. When ready to go, put back on the heat to warm up a bit and add the remaining cup of cream and continue as directed.