1 1/2 tablespoons, plus 2 tablespoons sugar
3 tablespoons water
1 tablespoon rum, kirsch, or amaretto liqueur
a few drops orange flower water, (optional)
6 slices brioche, challah or firm-textured white bread, such as pain de mie, cut in 1/2-inch (2cm) slices
6 ounces (170g) almond paste
2 large eggs, at room temperature
a few drops pure almond extract, (optional)
1/2-3/4 cup (40-60g) sliced almonds
In a small saucepan, heat the 1 1/2 tablespoons of sugar with the water, stirring until the sugar is dissolved. Remove from heat and add the liquor and a few drops of orange flower water, if using.
Preheat the oven to 425ºF (220ºC). Line a baking sheet with parchment paper (or leave it unlined) and place the slices of bread on it.
In the bowl of a stand mixer fitted with the paddle attachment, or by hand in a medium bowl with a spatula, beat the almond paste with the remaining 2 tablespoons of sugar, the eggs, and a few drops of almond extract, if using, at medium-high speed until smooth. But avoid whipping it up; mix it just until most of the lumps are removed. (A few little ones won’t matter.)
Brush each slice of bread generously with the syrup, enough so it saturates the bread all the way through. Spread each piece of bread with the almond topping then sprinkle sliced almonds over the top.
Bake until the tops of the Bostock are well-browned. I begin checking them at the 6-minute mark but they can take up to 10 to 12 minutes so best to rely on visual clues rather than precise minutes. Remove from the oven and sprinkle with powdered sugar. Serve warm or at room temperature.
Note: The almond topping can be made in advance and refrigerated up to one week. Let come to room temperature before using.