Combine the milk, carrots, onions, 1 TBSP parsley, thyme, and peppercorns in a large sauce pan.
Bring the milk to a simmer. Cook for 4-5 minutes.
Remove from the heat. Allow to steep for 10 minutes.
Strain the milk into another container.
Melt the butter in the large sauce pan.
Stir in the flour, mix to combine, and cook for about 30 seconds, stirring constantly.
Stir in the strained milk. Bring to a simmer, stirring regualry.
Set sauce aside while you prepare the bacon and lettuce. Keep on low to keep the sauce warm.