In a medium pan over medium-high heat, heat the olive oil. Mix in the onions and garlic; cook for 2 minutes until soft. Add the flour and mix well. Add the milk, mix well and Add the chopped spinach and warm through. Add the salt and pepper. Mix well.
In a pot with boiling water add the cleaned spinach and leave it in there for no more than 30 seconds, you just want to scald it. Take out the spinach and drain the water. Add the spinach to a food processor and pulse it only a couple times, you don't want it to turn into a puree.