Make the pie crust: In a food processor, pulse the flour, sugar, butter, and salt. (Alternately, cut the butter into the dry ingredients by hand using a pastry cutter or two knives.) When the butter pieces are the size of small peas, add 4 tablespoons ice-cold water. Pulse until combined. Add only enough water to hold the dough together. After a few tries, you’ll get a feel for it. Gather up the dough into a ball and flatten into a disk. Wrap in plastic film and refrigerate for at least 30 minutes and up to one day.

Spray muffin tin with cooking oil spray. Roll out pie dough to 1/8-inch thickness. Cut out circles, 4 inches in diameter. Carefully place your pie crust circles into the cavities of your muffin tin. Ease the crust into place so that it takes on the shape of your muffin tin. Chill for at least 30 minutes—or wrapped in plastic, overnight.

Make the berry filling: Combine sugar, lemon juice, zest, cornstarch, and half of the berries in a heavy-bottomed pot. Cook until juices have thickened. Stir in remaining berries until berries are well-coated with thickened juices. Allow to cool completely.

Make the streusel topping: Pulse all streusel ingredients in a food processor until combined. (Alternately, use a pastry cutter or two knives to cut the ingredients together until streusel is completely combined and your butter pieces are the size of peas.) Keep the streusel topping chilled until ready to use.

Fill chilled crusts to the top with cooled berry filling. Top each with 2 tablespoons of streusel.

Preheat oven to 375 degrees. Place muffin tin on a rimmed cookie sheet and bake for 30 minutes in lower third of oven, until filling is bubbling and crust is golden brown. Allow to cool slightly (about 15 minutes) before removing from pan with an offset spatula.