Typically, most Colombians will buy a box of Natilla mix, however, for those of us who find it a bit hard to head to the store for a mix, you can attempt to make it yourself. Here is the recipe.
4 cups milk -- use whole or 2%
1 cup brown sugar (in Colombia you would use 8 ounces of grated Panela)
4 - 5 cinnamon sticks
1/2 teaspoon baking soda
1/2 teaspoon salt
1 cup cornstarch
2 tablespoons butter
1 teaspoon vanilla
1. Mix milk and cornstarch in a pan.2. Add the brown sugar, cinnamon, baking soda and salt to the pan and mix well.
3. Heat the mixture over low heat, stirring constantly, until it starts to thicken.
4. Cook for 20-25 minutes, stirring constantly -- in order to avoid clumps, until mixture has thickened. It will get very thick and hard to stir and turn to a caramel color. DON'T LET IT BURN!
5. Once it is cooked and caramel in color, remove from the heat. Take out the cinnamon sticks and stir in the butter and vanilla.
6. Pour mixture into a buttered 8 inch square pan (glass works better) and let cool.
7. Cut into 2 inch square pieces and serve.