In a bowl, place the water, crumbled yeast, milk, sugar, flour, and 1 egg, then knead for 7 minutes.

Add butter in pieces and salt, then knead for 5 minutes. Place the dough on a floured work surface. Fold the edges of the dough towards the center, roll into a ball, place in a bowl, cover with a cloth and let rise for 1 to 2 hours at room temperature.

Place the dough on a lightly floured work surface and flatten it by hand. Shape it into a long roll, then divide it into eight balls. Arrange these balls on trays lined with parchment paper, making sure to space them 5 cm apart, cover with a cloth, and let rest for another hour.

Preheat the oven to 250 °C. Beat the remaining egg in a bowl and brush it over the buns. Sprinkle with sesame seeds, then bake for about 10 minutes. Let cool.

Divide the ground beef into eight small portions and cook them in a pan for 3 to 4 minutes with oil, season with salt and pepper.

Slice the buns in half, spread ketchup on the bottom, place the patties on the base, and cover with a slice of cheddar. Cut the remaining slices into teeth shapes for decoration. Add a slice of tomato on top of the cheddar and place the top half of the bun.

Slice the olives into rounds, and stick them on toothpicks and into the burgers to form eyes.