Squeeze spinach hard with your hands to remove as much water as possible. Place spinach on a cutting board, chop it roughly and set aside. Heat butter and olive oil in a large skillet over medium-high until butter foams. Reduce heat to medium, add shallots and cook, stirring, until shallots soften and begin to brown, two or three minutes.
Add spinach and season with salt, pepper and nutmeg to taste. Cook, stirring, until ingredients are combined and spinach is heated through. Remove from heat and add half and half, stirring to combine well. Serve immediately.