Melt 1 stick of the butter in a large skillet over medium heat. Add the garlic and onion and cook until the onion is softened, 2 to 3 minutes. Add the artichoke hearts and stir. Pour in the cream and bring to a boil. Reduce to a simmer and let the mixture thicken for 1 to 2 minutes. Season with salt and pepper. Stir in the cream cheese and Parmesan and mix until smooth. Add the spinach and cook, stirring occasionally, until the spinach is fully wilted. Set the mixture to cool to room temperature, about 20 minutes.
Preheat the oven to 375 degrees F.
Melt the remaining 1 stick butter in a small saucepan. Spray a baking sheet with nonstick cooking spray and set aside.
On a clean work surface, halve and trim the phyllo sheets into 18 rectangular pieces (5 1/3 inches by 9 inches). Layer 3 phyllo sheets, brushing the top of each layer with melted butter. (Cover the remaining phyllo dough with plastic wrap and a damp cloth to keep from drying out.) Place 1/4 cup of the filling about 1 inch from the bottom of the phyllo rectangle. Fold the corner of the phyllo dough over the filling, creating a triangular filled pocket. Continue to fold, keeping the triangle shape, until completely sealed. Place it sealed-side down on the prepared baking sheet. Repeat with the remaining phyllo sheets and filling until you have 6 hand pies.
Brush the top of the phyllo triangles with the remaining butter and bake until golden brown, about 15 minutes. Serve warm or at room temperature.