Lol I was about to link my guide before reading your post.
1500 calories is where I'm at currently on a cut and losing weight, so I take it what you're saying is if you stay at 1500, you'll lose more weight which is dangerous as you are currently underweight?
I would tell you to snack on nuts during the day. 100g of nuts contain 550 calories, they contain good oils and a lot of protein.
Otherwise, add oil to your cooking. Oil has 884 calories for 100g, so adding just two teaspoons of oil to your cooking quickly adds up to 100 calories. If you cook twice in a day, that's 200 extra calories.
But high fat consumption also leads to disease down the line, I don't remember the name right now but it's a problem known in some populations that cook with oil a lot (and other fats).
Is there something in your life or diet that makes you feel full so quickly, or has it been like this forever?
Everything else should be in the guide 😄