In a small saucepan, combine the fresh strawberries and sugar. Cook over medium heat, stirring occasionally, until the strawberries soften and release their juices.
Lightly mash the strawberries and continue cooking until the mixture thickens into a jam-like consistency. Remove from the heat and let it cool completely.
In a small bowl, combine the softened butter, granulated sugar , and all-purpose flour. Mix until crumbly, then set aside.
Mix the granulated sugar and melted butter until well combined.
Add the eggs and vanilla extract, then whisk until smooth.
Add the vegetable oil and mix until fully incorporated.
In a separate bowl, whisk together the all-purpose flour, baking powder, and salt.
Gradually add the dry ingredients to the wet ingredients and gently mix until just combined.
Add the milk and gently mix until a smooth batter forms. Avoid overmixing.
Divide the batter evenly among the paper-lined muffin cups.
Add a little strawberry jam over each muffin and gently swirl it into the batter.
Sprinkle the prepared streusel topping evenly over the muffins.
Bake until the muffins are golden and a toothpick inserted into the center comes out clean.
Let the muffins cool in the pan for a few minutes, then serve
