In a small saucepan, heat the unsalted butter and olive oil over medium heat until the butter melts.

Add the flour and cook, stirring constantly, for about 2 minutes.

Gradually stir in the milk, vegetable broth (or water), sherry, salt, pepper, and nutmeg.

Continue cooking and stirring constantly until the mixture thickens, becomes smooth, and starts to bubble.

Stir in the finely chopped pine nuts, raisins, and well-drained cooked spinach.

Cook for an additional 1 minute.

Let the mixture cool slightly, stirring to release steam.

Spread the mixture onto a dinner plate and let it cool completely.

Refrigerate until firm enough to handle.

Place the beaten egg and bread crumbs in separate shallow bowls.

Shape the spinach mixture into 1-inch balls.

Dip each croquette into the beaten egg, then dredge in the bread crumbs.

Place the coated croquettes on a plate and let them sit until dry for about 10 minutes.

Heat at least 1 inch of oil in a medium skillet over medium-high heat (or use a deep fryer set at 365°F) until it turns a cube of bread light brown in 60 seconds.

Place the croquettes in the hot oil and cook, turning several times, until they become golden.

Transfer the fried croquettes with a slotted spoon to paper towels to drain.

Serve hot.