Preheat the oven to 350ºF 180ºC/Gas 4/fan 160ºC.
Line a muffin tin with paper liners or spray with nonstick cooking spray.
In a large bowl of a stand mixer, cream the butter and sugar from the muffin ingredients.
Beat in the egg and the teaspoon of vanilla extract, and mix well.
In a separate medium bowl, add and whisk the 2 1/3 Cup flour, baking powder and salt, and stir to combine.
Add the dry ingredients to the wet ingredients alternatively with the half and half.
Last, add in the lime juice and lime zest until fully incorporated, but do not over-mix.
Pour muffin batter evenly (2/3 full) into a 12-greased or paper-lined muffin pan.
Combine the streusel topping ingredients
Cut in the butter until crumbly.
Top the muffins evenly with topping.
Bake for 25-30 minutes, until golden brown, let cool for 5 minutes before serving on a wire rack.
Serve and enjoy!