Pulse together flour, almonds, brown sugar, and salt in a food processor until nuts are finely chopped. Add butter and pulse just until blended. Coarsely crumble in a shallow baking pan and chill at least 1 hour.

Preheat oven to 425°F with rack in middle.

Scrape seeds from vanilla bean into a small heavy saucepan, then add pod and butter and cook over medium-low heat, swirling pan occasionally, until butter is browned and fragrant, about 4 minutes.

While butter browns, stir together sugars, flour, and a pinch of salt in a large bowl. Add pears and brandy and toss to combine.

Discard vanilla pod, then toss butter with pear mixture. Spoon filling into 6 gratin dishes and sprinkle with topping, mounding it slightly in centers. Put in a shallow baking pan and bake 30 minutes, then rotate baking sheet and bake until topping is golden brown and filling is bubbling, 10 to 15 minutes more. Cool to warm or room temperature on a rack.