Preheat the oven to 350 F (180 C).

Melt the butter in a pan over medium heat.
Sauté the zucchinis until they start to soften (3 minutes).
Add the garlic and stir.
Bring to medium heat and continue cooking for 1 minute or until the zucchinis are well cooked and the juice has evaporated.
Remove the pan from the heat, stir in the mint, season with salt and pepper to taste, and set aside.

Beat the egg and egg yolk with the cream until smooth. Season with salt.

Sprinkle the tart shell with crumbled feta cheese.
Pour half of the egg mixture over the cheese.
Add the zucchini mixture in a uniform layer and cover with the remaining egg mixture.

Place the tart on a baking sheet and bake in the lower third of the oven for 30 to 35 minutes or until the filling is set and lightly golden brown.
Let cool for 10 minutes before serving.