In a frying pan over medium heat melt 1/4 cup (50 grams) of butter.
Add the morel mushrooms, garlic, and sprigs of thyme. Sauté over low heat for 10 minutes.
Remove the sprigs of thyme and season with salt and pepper and set aside.
On another frying pan over medium heat, melt 1/8 cup (25 grams) of butter. Add red onions, apple cider vinegar, and sugar and let it cook for 10 minutes, stirring occasionally.
Spread the caramelized red onions and the morels over the base of the quiche crust.
Break 4 large eggs into a large mixing bowl, add sour cream, full cream milk, salt, and pepper, and whisk well.
Carefully pour the egg and sour cream mixture over the caramelized red onions and morels.
Bake the quiche at 350 degrees Fahrenheit (175 degrees Celsius) for about 40 minutes.
Serve with a fresh salad.