Reduce oven temperature to 375 degrees F.
Drain artichoke hearts, cut in half and set aside.
In a medium pan, sauté garlic, onions, red pepper and spinach until al dente. This releases any moisture in the veggies before they're added to the filling and it flavors them too.
Remove from heat and scoop into a bowl to cool slightly.
Add the artichoke hearts to the same pan and sauté lightly to release any remaining liquid. Then remove them from the heat and set aside.
In a large bowl, add the milk, cream, duck eggs, Gruyere and a pinch of pepper. Whisk to combine.
Add the red pepper veggie mixture to the heavy cream mixture and mix to combine. Don't add the artichoke hearts just yet.
Pour the mixture into the prepared crust.
Arrange the artichoke heart halves around the top of the quiche gently so they do not sink into the egg mixture.
Bake until mixture is set and firm in the center, about 40-45 minutes.
Cool for 5 minutes and serve.