Preheat your oven to 180 degrees C (350 degrees F).
Preheat a frying pan over medium-high heat, then add your spinach. Once the spinach has wilted, transfer it onto kitchen paper (paper towel) and set aside.
Wipe the inside of the pan with paper towel, or just clean it and get it back on the stove. Pre-heat the pan again over medium heat, then add your butter. Once the butter has melted and is bubbling, add your onions and saute them for about 2 minutes.
Add your garlic and saute for another minute. Grab your spinach, squeeze as much excess liquid out as you can, then roughly chop it up on a chopping board. Finally, add your spinach and stir it through the buttery onions and garlic. Turn the heat off and set aside.
Put your heavy whipping cream in a large bowl, then use a whisk or an electric beater to beat the cream until soft peaks (thick enough to barely hold it's shape). Put in the fridge until you're ready to use it.
Use your extra butter to grease the inside of your pie dish. If you want to remove the quiche at the end, I recommend lining the pie dish with baking paper (parchment paper) and then greasing that paper with more butter, or by using cooking spray or by brushing on some olive oil.
Crack your eggs into a large mixing bowl then whisk until all the egg is well beaten.
Add a small pinch of salt, a generous pinch of black pepper, your cheddar cheese, your Parmesan cheese, your sun dried tomatoes and your spinach, onion and garlic mixture. Stir everything together until well combined.
Get your bowl of heavy whipped cream, then add it to your egg mixture. Then, slowly fold the whipped cream through the egg until you have a light, well combined mixture.
Transfer your quiche mix to the greased/lined pie dish. Neatly place your asparagus on top and then bake in the oven for 35-40 minutes.
To test if the quiche is fully cooked, stick a skewer or a toothpick in the quiche and leave for 2 seconds. If the skewer or toothpick comes out clean, the quiche is ready to serve.