Preheat your oven to 325 degrees
Mix your butter, sugar, eggs, milk, sourdough discard and vanilla extract in a large mixing bowl.
Add the dry ingredients to wet ingredients and stir until just combined.
Fold in Berries and Cinnamon.
Grease your muffin tin, or add muffin liners to the muffin pan.
Divide the muffin batter into muffin pan
In a small bowl, mix Streusel by hand until the butter has broken down. You want it to be crumbly. Add about a tbsp to the top of each muffin.
Bake for 15-20 minutes. Check with toothpick. The top should be slightly brown.
Cool on a wire rack before eating. Store in an airtight container or freeze the extras if you can resist them.