2/3cupfresh strawberries, chopped into 1/2" pieces
2/3cupfresh or frozen rhubarb, chopped into 1/2" pieces
For the streusel:
1/4cupall purpose flour
2Tablespoonslight brown sugar
2Tablespoonsquick oats, or process large flake oats lightly to break down a bit
Pinchsalt
2Tablespoonsbutter, cold and cut into 2 pieces
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Instructions
Preheat oven to 425 F. (regular bake setting/not fan-assisted). Line 9 muffin cups with paper liners and set aside.
For the muffins: In a medium bowl, whisk together the flour, baking powder, baking soda and salt. Set aside.
In a large bowl with an electric mixer or the bowl of a stand mixer fitted with the paddle attachment, add the butter and white sugar and beat well for about 2 minutes at medium speed, scraping down and bowl as needed. Add the eggs one at a time, beating well between additions. Add the vanilla and sour cream and beat to combine. Add flour mixture, a bit at a time until all is added and incorporated. Don't over-mix. Fold in the chopped strawberries and rhubarb by hand.
Scoop batter into muffin cups.
For the streusel: Stir together the flour, brown sugar and oats in a medium bowl. Add the cold butter and using your fingertips, rub the butter into the dry mixture until you have a crumb with pea-sized pieces of butter.
Scatter the streusel overtop of the muffins, dividing between the 9 muffins.
Bake in preheated oven for 18-20 minutes, then check. If the streusel is already golden enough, loosely lay a piece of aluminum foil overtop. Continue baking another 5 minutes, or until a tester inserted in the centre comes out clean.
Allow the muffins to cool in the pan for a couple of minutes, then remove from the muffin tin onto a cooling rack to cool completely.
Notes
When you take the butter out of the fridge to come to room temperature, take the eggs and the sour cream out of the fridge as well, so they are at room temperature as well.
"Creaming" together the butter and sugar is a classic baking technique. Do this at medium speed (not high speed) and don't rush this part of the process, as it is important for the finished texture of the muffins.
If your mixture seems curdled after adding the eggs, this is generally due to a difference in temperature between the eggs (probably too cold) and the batter. To fix it, mix in a few tablespoons of the flour mixture, then proceed with the recipe.
Once you add the dry ingredients, mix only until combined (don't over-mix at the end).
I like to cut the rhubarb and strawberries fairly small for these muffins, but you can go chunkier if you like.
Be sure to read the notes above this Recipe Card, where you'll find ingredient and substitution notes, step-by-step photos and recipe tips!