Preheat oven to 400 degrees Fahrenheit or 200 degrees Celsius, and place your baking rack on the bottom slot of your oven.

Unroll your pie crust and line a 9-inch pie plate or tart pan.

If necessary, trim the edges of your dough so they don’t hang much over the edge of your pan. Fold the edges of the crust back and under so that you form a border at the top that does not go much over the edge of the pan. Any crust around those edges will just snap off when you try to remove the quiche slices.

Next, use a fork to prick the crust all over the bottom of the pan.

Line the crust with parchment paper and cover with pie weights, or raw rice or beans. This will ensure the bottom doesn’t puff up as it bakes.

Bake on the bottom oven rack for 20 minutes, then remove the parchment and weights, and bake for an additional 5 minutes. The edges of the crust should be golden, and the middle should no longer look raw.

While the pie shell is baking, heat butter in a small skillet over medium heat.

Add shallot slices and sauté for about 5-8 minutes, until starting to brown. Remove from heat.

Whisk together eggs, cream, mustard, salt, and pepper in a large bowl.

When crust has been removed from oven, spread the shallot slices on top, followed by the spinach, and half of the gruyère cheese.

Pour in the egg mixture.

Sprinkle with remaining cheese and grate nutmeg over the top.

Bake for 25-30 minutes on the bottom oven rack, or until the egg custard is cooked through and lightly browned on top. The filling should be completely set—if it jiggles when you touch the pan, it’s not done.

Wait to slice the quiche for at least 10-20 minutes—this will allow the quiche to fully set, and you’ll get cleaner slices.

Serve either warm or at room temperature.