Stay away from bacon burgers as a second dinner. Your protein intake should match your target weight of you are hitting the gym.
Peanut butter, per ounce, 165 calories, 116 from fat, 7g protein, 14g fat.
Roasted chicken breast, per ounce, 46 calories, 9 from fat, 9g protein, 1g fat.
80% lean hamburger, per ounce, 76 calories, 44 from fat, 8g protein, 5g fat.
Cooked bacon, slice, 43 calories, 30 from fat, 3g protein, 3g fat.
If you want to add weight, eat calorie dense foods that contain enough protein to help the work you're doing to put on the muscle you want easily, and don't consume too many calories in the process (not generally a big problem for 18 year olds who are working out consistently, and aren't living on junk food). What you eat, within those parameters, isn't especially important (again, assuming the not living on junk food part). The guys who are relying on chicken breasts and peanut butter on everything are just getting there via a different path (mine also eats chicken and PB, fwiw, along with insane amounts of fruit in his "milkshakes"). Chicken's great for lean protein, but good luck eating enough of it to get the calories you'll need to add weight (which is one reason why people who are trying to lose weight choose it, and likely why the guys above listing it are also throwing in the PB).