Heat 2 Tbsp olive oil in a saute pan over medium heat.
Add the diced bacon and slowly render the fat until the bacon is crispy, about 10 minutes.
Remove the cooked bacon from the pan with a slotted spoon. Then, add the diced onion to the pan and sauté in the bacon fat until tender and translucent, about 5 minutes.
Add the minced garlic and cook for an additional 2 minutes.
Next, sprinkle the flour over the onion/garlic mixture.
Simultaneously, pour the milk and heavy cream into the saute pan while stirrring with a wooden spoon to ensure there are no flour chunks.
Cook over medium low heat until the mixture has thickened slightly.
Then, add the raw spinach to the mixture. Cook on low until spinach is completely wilted.
Add bacon crumbles back to the spinach along with freshly grated lemon zest.
Season with salt & pepper to taste.