Preheat the oven to 200°C (390°F) using conventional oven settings (top and bottom heat). Halve the onions, peel them, and slice them into thin rings. Heat oil in a pan, add the onions and salt, and sauté over medium-high heat for a total of 15 minutes, stirring regularly. As soon as you feel the onions are starting to burn, deglaze the pan with one to two tablespoons of warm water. Repeat this process whenever the onions become dry. The onions are done when they are golden brown, very soft, have a sweet aroma, and have reduced in size by about two-thirds.

Meanwhile, wash the spinach or kale and drain well. Dissolve the stock cube in 250 milliliters of hot water.

After about 15 minutes, or as soon as the onions have turned golden brown and lost about 2/3 of their volume, add the cream cheese and deglaze the pan with the vegetable broth, stirring well until the cream cheese has dissolved.

Add the beans, gnocchi, and spinach or kale to the pan and stir well until the spinach leaves have wilted. Season the gnocchi mixture with salt and pepper.

Turn off the stove, spread the cheese over the pan and put the gnocchi casserole in the oven for about 20 minutes at 200°C (top/bottom heat), or until the cheese has melted and formed a light golden crust.