Boil coffee grounds in 1 1/2 cups of water.

Remove from heat and let sit for 10 minutes to infuse.

Bring milk and half-and-half to a simmer.

Strain coffee liquid through a coffee filter.

Add 3/4 cup of strained coffee to the milk mixture and heat through.

In a separate bowl, whisk together eggs, sugar, and salt.

Slowly add the milk mixture to the egg mixture, whisking constantly.

Pour 1 tbsp of caramel into each of 6 buttered 6 oz ramekins.

Pour the custard mixture into the ramekins.

Place the ramekins in a large, high-walled pan.

Fill the pan with water to create a water bath (bain-marie).

Bake at 325°F (160°C) for 1 hour.

Increase the oven temperature to 375°F (190°C) and bake for an additional 20 minutes.

Remove the ramekins from the oven and water bath.

Refrigerate for at least 4 hours to chill completely.

Use a flexible knife to loosen the flan from the ramekins.

Invert the flan onto small plates for serving.