At 15 months, he should be having a varieties of food. Doesn't matter if it's only 2 teeth. Cook the food ie meat awhile longer or cut to smaller pieces. There are soft veggies around ie broccoli, cauliflower, potatoes, carrots etc. No need to be mashed. Small soft chucks are good.
I suggest giving him a variety of food. Steam vegetables and meat. Cereal, mashed potato, yogurt with fruits, salmon. Everything can just be steamed and served.
At 15 months can eat most things. I feed mine scrambled eggs, fruits, porridge, pancakes, cereals (not crunchy)
They can eat everything already. Don't worry. My boy has no teeth and I feed him everything :)
Pancakes? French Toast. Scrambled eggs. The above alternatives are yummy!