Adjust an oven rack to the middle position and set the oven to broil on high.
In an ovenproof 12-inch nonstick skillet set over medium heat, add the bacon and cook until just crisp, 4 to 5 minutes. Set aside. Add the sausage to the skillet and cook, breaking it up, until well browned, about 6 minutes. Add the sausage to the bacon, leaving behind the pork fat in the skillet.
In a bowl, whisk the eggs and half-and-half together. Add the egg mixture to the skillet with the pork fat and cook over medium heat, stirring with a rubber spatula, scraping and tilting the skillet to slide the egg mixture around the skillet, until the bottom is set and the top is still wet and glistening, 2 to 3 minutes. Add the cooked meats and cheeses and season with salt and pepper. Use a spatula and press the ingredients into the eggs.
Place the skillet in the oven and cook until lightly golden on top and puffed up, 2 to 4 minutes. Let the frittata rest for about 5 minutes before slicing. Slide the frittata on a cutting board and cut into wedges roughly the size of each croissant.
Schmear the cut side of each croissant half with Giardiniera Chive Cream Cheese. Lay a couple of tomato slices right on there. Place a big wedge of frittata on each croissant. Close up and eat!
Giardiniera Chive Cream Cheese:
Using a fork or small mesh sieve, drain the giardiniera from the jar and let most of its oil drip back into the jar. Place the drained giardiniera into a bowl with the softened cream cheese, chives and honey. Season with salt and pepper. Whisk vigorously until light and smooth. Season to taste.