In a mixing bowl, combine 1 cup of flour, 1/2 cup of cold butter cut into cubes, and 1/4 cup of sugar. Use a pastry cutter or your fingers to blend until the mixture resembles coarse crumbs. Press the dough into mini tartlet molds, ensuring an even layer. Preheat your oven to 350°F (175°C) and bake for 10-12 minutes until they turn lightly golden.

While the tartlet shells cool, prepare the filling by blending 1 cup of cooked pistachios, 1/2 cup of sugar, 1/4 cup of softened butter, and 2 eggs in a food processor. Pulse until the mixture is smooth and creamy, scraping down the sides as needed.

Once the tartlet shells have completely cooled, spoon or pipe the pistachio cream into each shell, filling them generously. Use a spatula or a piping bag to smooth the top.

After filling the tartlet shells, place them in the refrigerator to chill for at least 30 minutes.

Once chilled, remove the mini pistachio tartlets from the refrigerator and arrange them on a tiered dessert stand or a decorative plate. Garnish with fresh berries or edible flowers if desired.