Step 1

Spray a slow cooker with nonstick spray. (You'll thank me for this at cleanup time!)

Step 2

Add potatoes, onion, and salt and pepper and stir to mix.

Step 3

In a small saucepan melt butter over medium high heat.

Step 4

Add flour whisking constantly for about 1 minute.

Step 5

Slowly add milk, continuing to whisk.

Step 6

Add cheeses and continue stirring until melted.

Step 7

Remove from heat and pour over potatoes.

Step 8

Cover and cook on high 4-5 hours. Serve warm.