TL/DR: You must change your goals and mindset so that you can gain lean weight in sustainable manner - longterm. If you gain 7kg in one month, it will be either mostly water retention (bloating) or fat. Fat can not be converted to muscle. Any fat gained will make it harder to gain muscle by worsening your insulin resistance.
One meal of 1600kcal is not healthy. I hope you mean it's 300gr in weight, not 300gr of protein in single meal. The protein from that meal will not be absorbed properly (in single portion depending on number of conditions you maybe can absorb something in the range of 20-50gr of protein, unless you have extraordinary genetics or have fasted for long). Such huge meal will probably make you feel sick and you will most likely not have any appetite for most of the day. After several days of trying to push that much calories in - you will feel sick from the thought of eating any more.
If you however manage to consume that much calories (which again I highly doubt), you could in fact gain 7kg in a month - the problem is that most of them (5 or more) will be just fat. That will not make you look better and is not healthy at all. You will worsen your insulin resistance and will rise your cholesterol levels at the very least.
Realistically, with average genetics you can gain just about 1-1.5kg of lean weight per month, with proper resistance (weight) training and nutrition. However if you gain 7kg of lean mass over the course of 6 months, you will look much bigger, it will be healthy.
So focus on increasing your caloric intake by up to 30% over your burn rate as a start. Eat 3-4 times a day - balanced, protein rich meals and maybe have a protein shake here and there if it helps you boost your calories.