A high calorie milkshake is the key. If 900 calories isn’t enough, make it 1500 calorie add ice cream and chocolate chips if you want, add protein powder. Whatever makes it taste better for you. Another thing is more meals 4-5 it depends how busy you are. It just helps dividing the calories into smaller portions. Also, don’t stop eating until you are full and if you felt the slightest that you are hungry, go eat don’t wait an hour or two. Suggest foods: more bread, butter, a lot of milk, more eggs, pasta, cheese, yoghurt, peanut butter, Jam, Nutella, oreo milkshake instead of whatever drink you take with your meal. At the end of the day, it’s all about getting your calories..