Prepare your bacon if you do not already have it available.
Cook the garlic in the bacon grease and ¼ cup of beer in a medium saucepan over medium heat until the garlic is fragrant. Mix another ¼ cup of the beer with the cornstarch and lemon juice to make a slurry. Add this to the saucepan and cook until the slurry is incorporated.
Add in the remaining beer and the milk, cook until the mixture begins to thicken.
Add the cheese, one cup at a time and mix until melted. stir in the mustard, the bacon grease, and ¾ of the crumbled bacon, if using. Transfer to a serving bowl and top with the remaining bacon.
Serve warm.
Notes
If you are making bacon especially for this dip, I recommend baking the bacon in the oven at 400F for 15 minutes. No need to cool the bacon grease before using. Take your time adding the cheese and stirring. It can very easily become grainy in texture. Do not overheat the mixture and stir until just combined and the cheese is fully melted.Nutritional values are if you do not use bacon pieces, but do use bacon grease or butter