Start to finish: 35 minutes
Makes: 3 cups
10 ounces chopped, frozen spinach
1 pound white cheddar cheese, cubed
8-ounce block cream cheese
½ cup sour cream
15-ounce can chopped tomatoes, drained
Thaw spinach to package instructions in a colander lined with a thin towel. Once thawed, use towel to squeeze moisture out of spinach. Set aside.
In a heavy-bottomed pot over medium-low heat, combine all ingredients. Stir every few minutes until smooth and fully melted, about 25 minutes.
Slow cooker: Follow instructions as listed above, except using a slow cooker on the high setting. Stir every 20 minutes until smooth and fully melted, about 1.5 hours. Serve on warm setting.