Preheat the oven to 350 degrees.
Mix the eggs in a bowl with a fork and then add the cheese, basil, milk, salt and pepper.
Stir to combine and then set aside.
Heat the oil in a 10-inch cast iron or non-stick skillet. Either way, make sure it’s oven safe.
Add the onions and garlic then cook until soft, about 5 minutes.
Turn off the heat and then place the squash blossoms in the pan.
Stir the egg mixture one last time and then pour the mixture into the pan and then loosely cover with foil.
Place the entire pan in the oven and let cook for about 20 minutes until the center is no longer giggly.
When the frittata is done cooking, remove from the oven.
Loosen the sides with a spatula or knife and slice.
Serve warm, at room temperature, or cool.