Preheat the oven to 350°F (175°C).

Heat butter and olive oil in a skillet over medium heat; it should shimmer and smell warm.

Add the chopped onion and garlic, and sauté until the onion is translucent and soft, about 4–5 minutes, stirring so the garlic doesn’t brown.

Add the drained spinach and cook for 2–3 minutes until any remaining moisture evaporates and you can smell the greens.

In a mixing bowl, combine cream cheese, heavy cream, sour cream, Parmesan, salt, pepper, and nutmeg; whisk until smooth and slightly glossy.

Fold the warm spinach into the cream mixture and stir until well combined; taste and add a dash of hot sauce if you want a lift.

Transfer the mixture to an oven-safe dish and smooth the top with a spatula.

Bake until hot and bubbling and the edges show a light golden color, about 18–22 minutes.

Let it rest for 5 minutes before serving so it firms up slightly; it should be spoonable and creamy.

If you want a crisp topping, broil for 1–2 minutes at the end, watching closely.