Place the frozen deep-dish pie crust on a baking sheet.
Sauté the Onions & Garlic
In a small saucepan, melt butter over medium heat.
Add diced onions and cook until soft, about 2-3 minutes.
Stir in garlic and cook for 30-60 seconds until fragrant.
Remove from heat and let it cool slightly.
Make the Egg Mixture
Whisk together eggs, half-and-half, thyme, salt, and pepper in a large bowl until smooth.
Stir in the onion mixture, ham, and both cheeses.
Assemble & Bake
Pour the mixture into the pie crust and spread evenly.
Bake for 40-45 minutes until the center is set and a knife inserted in the middle comes out clean.
Serve & Enjoy
Let the quiche cool slightly before slicing.
Serve warm or chilled with optional chopped chives or green onions.
Notes
Refrigerate: Store leftovers in an airtight container for up to 4 days.Freeze: Let the quiche cool completely, then wrap tightly in plastic wrap and foil. Freeze for up to 2 months.Reheat: Check out my tutorial on How To Reheat Quiche. Make-ahead: Assemble the quiche, cover, and refrigerate overnight before baking the next day.