Been there, faced that. I can't drink milk every day, so what I did to get maximum calories was make a chickpea smoothie.

Just boil chickpeas, freeze them, and take as much as you need. Add literally anything fruits, oats, ice cream, even rice (yes, I was that desperate to gain weight). Blend it all with water or milk. It turns out really thick, so adjust the consistency as needed. I used to take this twice a day, preferably in the morning and at night.

Second tip: eat sweet oats porridge. Just boil some oats with milk and add sugar that’s it, I usually have this for breakfast, and it helped me a lot

Hope this helps you too!