Boil half a cup of water in saucepan. Remove the bark from the pumpkin leaves and chop roughly. Add the baking soda to the water and add the pumpkin leaves, reduce heat to medium and cook for 10 minutes. Remove from heat and drain.

Cook pasta according to package instructions. Drain.

Heat 1 tablespoon olive oil on high heat in a large skillet, when oil is heated, add sliced onions and cook on high heat for about 10 minutes, constantly stirring with spatula. The onions should start to brown, but without burning (a couple of onions may be burnt here and there, but overall they should not be charred).

Reduce heat to medium and continue cooking onions for 10 more minutes, continuing to stir, as onions brown even more without burning. At this point add just a pinch of salt over onions.

Continue cooking for 10 more minutes on medium or low heat, stirring occasionally to make sure onions don’t stick to the bottom of the pan or burn. Total you should have cooked onions for 30 minutes.

Remove from heat and sprinkle onions with a small amount of balsamic vinegar to deglaze the pan. Using spatula, mix the onions, scraping the bottom of the pan and coating onions with a pinch of balsamic vinegar you just added.

Add heavy cream, milk, Parmesan cheese and 1/4 teaspoon salt to the onions-pumpkin leaves mixture on medium-low heat and mix. Add pasta to the creamy sauce, stir to coat on low heat for about 5-10 minutes until Parmesan cheese melts and starts to coat pasta as well.