Preheat the oven to 350F(180C).
Melt the butter.
Roughly mush the bananas. Set aside.
In a separate bowl, sift the flour. Add baking soda, baking powder, salt, and sugar. Mix.
To the bowl with the mashed bananas, add the melted butter and two eggs. Whisk until everything is incorporated.
Combine wet and dry ingredients. Fold gently until it becomes a batter.
Line a muffin pan with paper or silicon cups.
Take 2/3 of the dulce de leche (or 100 grams) for the filling. Save the rest for the topping.
Fill each cup halfway with the batter. Then add about a teaspoon (or more) of dulce de leche to the center of each cup. Top it off with more batter, just enough to cover the filling. Don't fill until the top of the cup.
To the rest of the dulce de leche, add about 30 grams (2-3 tablespoons) heavy cream or milk. Start with one teaspoon at a time. Mix until creamy. It should have the consistency of buttercream, not too loose but spreadable.
Top each muffin with about a teaspoon of the dulce de leche cream. Using a toothpick, spread the cream over the top( see photos).
Bake on the middle rack for about 35-40 minutes. depending on your oven. Check after 25min by inserting a toothpick into a muffin. If it comes out clean, the muffins are ready.
Let them cool on a cooling rack. Enjoy.