In a large skillet, combine sugar, flour, and baking soda (if using) over low heat.

Stir constantly until the sugar melts and turns a light golden brown color. Be careful not to burn the sugar.

Remove from heat and slowly whisk in the diluted evaporated milk. The mixture will bubble vigorously – be careful of splatters.

Continue whisking until the mixture is smooth and thickened.

Stir in the butter until melted.

Pour the caramel sauce into the bottom of four ramekins or a shallow baking dish.

Tilt the dish to coat the bottom evenly.

In a separate bowl, whisk together the eggs and vanilla extract.

Whisk in the evaporated milk until well combined.

Strain the custard mixture through a fine-mesh sieve to remove any lumps.

Preheat your oven to 350°F (175°C).

Place the ramekins or baking dish containing the custard mixture into a larger pan filled with enough hot water to reach halfway up the sides (water bath).

Bake for 30-35 minutes, or until a toothpick inserted into the center of the custard comes out clean. The custard should be set but still slightly jiggly.

Remove the ramekins or baking dish from the water bath and let cool completely at room temperature.

Once cool, cover the dish(es) with plastic wrap and refrigerate for at least 4 hours, or preferably overnight.

To unmold the pudding, run a knife around the edges of the ramekins to loosen the custard. Invert each ramekin onto a serving plate.

If using a baking dish, cut the custard into squares and serve.