In a large mixing bowl, combine flour, baking soda, cocoa powder, sugar and salt until thoroughly mixed.
Form a well in the middle of the dry ingredients.
Add the oil (or applesauce if substituting), vanilla extract, lemon juice and cold water.
Stir until completely combined and free of lumps.
Grease the muffin tins with oil or nonstick spray, or line with parchment cups.
Fill each well to about three-quarters full.
Place the muffin tins in the center rack of the oven and bake for 20-25 minutes.
While the cupcakes are baking, start your strawberry filling.
Over medium heat, add the chopped strawberries to a saucepan and stir constantly as they heat up and begin to soften.
When the strawberries are mostly liquid, add the sugar and cornstarch.
Continue to stir constantly for a few minutes more as the mixture thickens to a jelly-like in consistency.
Remove from heat, transfer to a bowl and allow to cool.
When the cupcakes are done — check that a toothpick inserted in the center of one cupcake comes out clean — transfer the tins to a wire rack to cool.
After the cupcakes have cooled, prepare them for the filling.
Using a paring knife, cut a cone out of the top of each cupcake, going deep enough to allow plenty of filling but not so deep that you cut through to the bottom.
Remove the cone and fill the space with the strawberry mix almost to the top but not quite.
Cut the “iceberg” portion off the cone you pulled from the cupcake so you have just the thin disk for the top and replace the “lid” over the strawberry filling.
Decorate with a little powdered sugar or sliced strawberries, and serve.
