Preheat oven to 425?F. Line a baking sheet with parchment paper and set aside.

In a bowl, mix 1/4 cup sugar and 1 tsp cinnamon. Set aside.

In a medium saucepan over medium heat, combine water, butter, brown sugar, and salt. Heat until butter melts and mixture comes to a boil.

Remove from heat and mix in flour with a wooden spoon until the mixture pulls away from the sides of the pot.

In three additions, slowly add in the beaten eggs, mixing well before the next addition.

Form balls with the dough, about 1 inch in size, and place them on the parchment-lined baking sheet.

Bake for 10-12 minutes, or until churros are golden brown. Remove from oven and roll in the sugar/cinnamon mixture while still hot.

For dulce de leche, combine milk, sugar, and optional salt in a large pot. Bring to a simmer over medium heat, stirring occasionally.

Remove from heat and stir in the baking soda dissolved in water, being careful as the milk might foam up.

Return pot to heat and bring to a low simmer. Do not boil. Check the mixture every 15 minutes, stirring to prevent burning on the bottom. Cook for 1-1.5 hours until the mixture turns golden brown.

Store dulce de leche in a jar in the refrigerator for up to 4 weeks.