Special equipment: a 12-cup muffin tin
Preheat the oven to 350 degrees F. Brush the cups of a 12-cup muffin tin with 1 tablespoon of the melted butter.
On a clean work surface, lay out the first sheet of phyllo pastry. Gently brush it all over with 1 tablespoon of the melted butter. Place the second phyllo sheet on top and brush it with another tablespoon of the melted butter. Continue stacking and brushing until all four sheets have been used, making sure to brush the top of the fourth sheet with the remaining tablespoon melted butter. Using a pizza cutter or a sharp knife, cut the layered phyllo sheets into 12 squares. If the phyllo is portrait-oriented to you, cut it into three columns lengthwise and 4 rows across (just like the muffin tin).
Line each muffin cup with a square of the phyllo and crack an egg into each phyllo-lined cup. Top each egg with a wedge of cheese and a small piece of prosciutto. Sprinkle about 1/8 teaspoon of the herbes de Provence, if using, over each tart.
Bake until the phyllo is golden brown and the whites of the eggs are set, about 15 minutes. (If you like your egg yolk fully cooked, be sure to bake your tarts for a couple more minutes.)
Let cool for 5 to 10 minutes, then carefully lift each tart from the tin with a small spatula. Enjoy warm or at room temperature.