You can pulse all strusel ingredients in a food processor just until they look like crumbs or alternatively mix in a bowl with a fork or pastry cutter. I used the food proceddor. Set aside

In a large bowl whisk flour, baking soda, cinnamon an salt until blended

In another bowl whisk sugar, egg and vanilla until combined

Slowly whisk in the butter and mix until well combinrd

Add sour cream and whisk until just smooth, don't overmix

Add blueberries to flour mixture and stir gently to coat them. This helps them not to settle on bottom of muffins

Slowly fold sour cream mixture into flour mixture sing a sparula. Batter will be thick, mix until just blended

Spoon batter equally into pans.

Sprinkle strusel evenly among tops of batter. Bake about 30 to 35 minutes for standard size muffins and 34 to 36 minutes for jumbo until they spring back when touched and a toothpick comes out with just a few moist crumbs but not any batter. Cool in pan 5 minutes then remove to racks to cool completely

Have white chocolate, chopped in a bowl. Heat cream until hot but not boiling and pour over chocolate, add vanilla. Let stand 1 minute then stir smooth.. Allow to cool to thicken, at room temperature about 25 mins or refrigerate, stirring often until thick enough to drizzle

Drizzle white chocolate over mufins.