Cream together sugar and softened butter until light and fluffy, about 2-3 minutes. Add eggs and vanilla, mixing until combined. Gradually incorporate flour and salt until smooth dough forms.

Cover the dough with plastic wrap and refrigerate for at least 30 minutes.

Preheat your oven to 350°F (175°C). Scoop tablespoon-sized amounts of dough onto ungreased baking sheets, spacing them 2 inches apart. Bake for 12-15 minutes until edges are lightly golden.

For the pastry cream, heat heavy cream with vanilla until just about to simmer. Whisk together egg yolks and sugar until smooth. Gradually pour in hot cream, whisking constantly. Return to heat until thick, about 5 minutes.

Once cooled, pipe pastry cream onto the flat side of half the cookies and top with the remaining cookies.

Sprinkle sugar on top of each filled cookie. Using a kitchen torch, caramelize the sugar until bubbly and golden. Alternatively, place under a broiler for 1-2 minutes, watching closely.

Allow cookies to cool so sugar hardens, serve at room temperature.