Heat butter over medium low heat in a medium sized sauce pan. Whisk in the flour and whisk and cook until smooth and bubbly, about 5 minutes.
Gradually whisk in one cup of milk, slowly. Add the salt and pepper. Bring the mixture to a boil, whisking constantly.
Remove from heat and stir in the two types of cheese. Combine until melted. Stir in the artichokes and spinach. Add the additional milk and return to heat and warm through.
Heat oven to 350 degrees. Lightly spray a muffin pan with non stick spray.
Cut 3 circles out of each tortilla. Press each circle into the bottom of each muffin cup. Bake for 8 - 10 minutes until the cups are golden and slightly crisp.
Remove the pan from the oven. Fill each cup with a generous portion of spinach artichoke dip. Sprinkle with additional Monterey jack cheese. Return to the oven and broil for 2 - 3 minutes until the cheese is bubbly and golden.
Transfer the tortilla cups to a wire rack. Repeat with the process with another 12 cups. Serve warm.
Notes
These are best served warm + fresh so the shell stays crisp. They can be reheated, but please note the shell will be soft.