In large slow cooker, add potatoes, onions, cooked bacon and 3 cups chicken broth; stir to combine.
Cook on low for 6 to 8 hours or on high for 3 to 4 hours, until the potatoes are fork tender and cooked through.
Just before serving, melt the butter in a small saucepan over medium-high heat.
Whisk in the flour until it is completely combined; cook for 1 minute, stirring occasionally.
Gradually add the evaporated milk and continue whisking until the mixture is completely smooth. Continue cooking until mixture reaches a simmer and thickens considerably, stirring constantly.
Immediately pour mixture into the slow cooker and stir until combined.
Add the cheddar cheese, sour cream or yogurt, salt and pepper; stir until combined.
Serve warm with desired toppings.
Tip: If you would like the soup to be even thicker, you can use a potato masher or a large spoon to mash about half of the potatoes (while the soup is still in the slow cooker) to thicken the soup. If you would like the soup to be thinner, add in an extra 1 to 2 cups of warmed milk or broth
Note: This recipe will not freeze well.