Melt 1 Tbsp butter over medium heat. Whisk in the flour and cook, stirring constantly, for about 2 minutes, but don’t let it turn brown. Add the milk and herbs and cook, stirring from time to time, about 10 minutes. Fish out the herb sprigs and transfer to a bowl to cool.
Top each slice of bread with a slice of canadian bacon. Mix together 1/4 of the Gruyere cheese and the bechamel sauce. Taste for seasoning. Spread a little of the sauce on top of the bacon and repeat with the other slices of bread.
Heat two large cast iron or nonstick skillets and crack 4 eggs into each skillet. While the eggs cook, place the crostini under the broiler and broil until the top becomes golden, 1 to 2 minutes. Season the eggs with salt and top each crostini with 2 fried eggs. Enjoy!