2 zucchinis, sliced into 1/4" rounds
1 1/2 teaspoons salt, divided
1 tablespoon olive oil
1 pound lean ground beef
1 onion, small dice
3 cloves garlic, minced
3 tablespoons fresh thyme, finely chopped
2 tablespoons butter
2 tablespoons flour
1 1/2 cups milk
2 cups mozzarella cheese, divided
Preheat oven to 375 degrees Fahrenheit and grease a 9-by-13 casserole dish.
Place zucchini rounds into a colander in the sink and sprinkle with 1 teaspoon of salt. Toss and let zucchini sit for 15 minutes until they release some moisture. When done, pat dry with paper towels.
Heat olive oil in a frying pan over medium heat. When hot, add the ground beef, breaking it up as you do.
Cook ground beef for 7 to 10 minutes, until no longer pink.
Add the onion, garlic, thyme, and remaining 1/2 teaspoon of salt to the frying pan. Stir and cook for 3 more minutes.
Heat butter in a medium-sized saucepan over medium heat.
When butter has melted sprinkle in flour and whisk to break up lumps. Let flour cook for 2 minutes.
Slowly add in the milk, whisking as you do to prevent lumps from forming.
Bring milk to a simmer and continue simmering for 10 minutes until thickened slightly.
Remove milk mixture from heat and slowly add in 1 1/2 cups of mozzarella cheese.
Place zucchini, ground beef, and cheese sauce into a large bowl and stir to combine. Pour into prepared casserole dish.
Top casserole with remaining 1/2 cup of mozzarella cheese.
Place in preheated oven and bake for 30 minutes, until entire casserole is hot and bubbling throughout and cheese on top has melted and is starting to brown.