helping my toddler gain weight

Kii • Mama to Bram and Waylon💛

HI my son is vegan as am I and his father but he's in the 20th percentile. he is 22lbs and 20months but he has always been very long and skinny. he eats tons of avocado and banana potato and sweet potatoe. quinoa and green veggies and beans. he loves chickpeas. anyways what are some other fat rich foods or beverages he can eat to help him gain weight faster? he drinks almond milk right now but mostly water or diluted apple juice.