Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a mixing bowl, cream together softened unsalted butter and granulated sugar until light and fluffy, about 3-4 minutes.

Add in the large egg and vanilla extract, beating until fully incorporated, about 1-2 minutes.

In a separate bowl, whisk together all-purpose flour, baking soda, salt, ground cinnamon, and ground nutmeg.

Gradually mix the dry ingredients into the wet, just until a dough forms, avoiding overmixing.

Scoop out portions of dough and roll them into 1-inch balls, spacing them 2 inches apart on the baking sheet.

Flatten each dough ball into a thick disk, about 1/2 inch high.

Bake for 10-12 minutes or until the edges turn golden brown.

Cool the cookies on the baking sheet for 5 minutes before transferring to a wire rack.

In a saucepan, simmer heavy cream over low heat, whisking in brown sugar and cornstarch until thickened, about 3-5 minutes.

Spoon the topping onto each cooled cookie and let set for a few minutes.

Broil the cookies for 1-2 minutes until the topping bubbles and caramelizes, watching closely.

Allow to cool completely for about 10 minutes before serving.