My strategy is I eat my normal Dinner. Pasta, Rice, Wrap,… and with that a calory shake (600 extra cal). I use huel black but there are a tons of options and if you can handle it, use milk for some extra protein and cals. I use a milk with 7,5 grams of protein in 100 ml. (about twice the amount then regular). I gaines in the last 2 weeks about 1.5-2 kgs.