https://feedgrump.com/tim-hortons-blueberry-muffins/

Streusel
30g all-purpose flour
2 tablespoons packed brown sugar
1 tablespoon granulated sugar
1 1/2 tablespoons butter, melted and cooled
Muffin Batter
188g all-purpose flour
150g granulated sugar
1/2 teaspoon kosher salt
2 teaspoons baking powder
60ml olive oil
1 large egg
125g milk
1 teaspoon vanilla
148g blueberries (frozen increase baking time by 5 minutes)

30 g all-purpose flour 2 tablespoons packed brown sugar 1 tablespoon granulated sugar 1 1/2 tablespoons butter, melted and cooled 188 g all-purpose flour 150 g granulated sugar 1/2 teaspoon kosher salt 2 teaspoons baking powder 60 ml olive oil 1 large egg 125 g milk 1 teaspoon vanilla 148 g blueberries (frozen increase baking time by 5 minutes)

Make streusel, set aside.
Oven 400F.
Makes 8 muffins, add a tablespoon water to empty slots.
Bake the muffins for 15 to 20 minutes, til tops are no longer wet.
Mix all dry in one bowl, wet in another, combine JUST until combined.
Fold blueberries in gently.
Top with streusel.