Use a food mill to process raspberries and remove seeds; discard seeds.
Alternatively, you can puree raspberries in a food processor, then strain to remove seeds; makes about 1 cup raspberry puree.
In a medium bowl, whisk together raspberry puree and sugar, until sugar is dissolved; stir in lemon juice and chill (makes about 1/2 cup syrup and can be stored up to 3 days in the refrigerator).
Cut a sheet of waxed paper to wrap around a one quart souffle dish; fold in thirds, lengthwise, so it is about 4 inches wide; wrap around the souffle dish and tape ends together, like a collar, so it extends the "height" of the dish by 3 inches; chill dish in freezer.
Alternatively, use the same method to increase the "height" of 8 individual ramekins by 1 1/2 inches.
In a large saucepan, over medium heat, cook peaches, 1/3 cup sugar and the lemon juice, stirring frequently, until peaches are soft and break down to an applesauce consistency, about 15 minutes.
Puree the cooked peaches in a food mill or blender; you'll have about 2 cups.
In a small saucepan, over medium heat, warm peach liqueur, stir in gelatin and cook, while stirring, until the gelatin melts; stir the gelatin mixture and the almond extract into the peach puree; chill until cold.
Bring a pot of water to a simmer; beat egg yolks with remaining 2/3 cups sugar in a mixing bowl.
Place mixing bowl over the simmering water, being sure the bowl does not touch the water; whisk egg yolks until they are pale yellow and have doubled in volume, 5 to 7 minutes.
Remove bowl from heat, whisk in the peach mixture and whisk until it cools down.
Beat egg whites to stiff peaks; in a separate bowl, beat whipping cream to soft peaks.
Stir half the egg whites into the peach mixture; add remaining egg whites to the whipped cream, then pour the peach mixture on top.
Gently fold them all together.
Gently spoon mixture into the souffle dish or the prepared ramekins; it should come at least halfway up the paper collar.
Smooth out the top and scatter with the toasted almonds.
Freeze until very firm, at least 4 hours; it can be frozen overnight, but transfer to the refrigerator for an hour to soften before serving.
If you do make it more than 1 day in advance, press plastic wrap to surface, once frozen.
To serve, carefully remove collar, serve thin slices with a little raspberry sauce spooned over, and the rest passed.
Alternatively, serve in individual ramekins, with a little raspberry sauce.