Butter 2 baking sheets, each 12 by 15 inches, or 1 baking sheet and a 14-inch pizza pan. Also butter the outside of a bowl that's about 4 inches deep and 7 inches wide at top. Invert bowl over a large juice can or other steady object at least 5 inches tall. Gently press an 18-inch square of cooking parchment (or heavy foil) over bowl. Butter a long, slender metal spatula.
Place coconut and almonds on another 12- by 15-inch baking sheet. Bake in a 350° oven until golden, 5 to 7 minutes; stir 2 or 3 times. Pour coconut and almonds into a bowl, add vanilla, and mix.
In a 1 1/2- to 2-quart pan over high heat, bring 1/4 cup water, sugar, corn syrup, and 6 tablespoons butter to a boil, stirring until butter melts. Boil over medium-high heat without stirring until the mixture reaches 300° on a thermometer, about 10 minutes. Quickly stir in the coconut mixture.
Working quickly, pour about 3/4 of the toffee, for bowl, onto 1 baking sheet or pizza pan. Pour remaining toffee onto the other sheet. Quickly spread toffee in both pans fairly thin.
When large piece of toffee is cool enough to touch, pull with your hands into an even, 11- to 12-inch-wide round (a few small holes are not a problem). Let round cool until it starts to firm but is still pliable, 1 to 3 minutes. Slide buttered spatula under round to loosen, then lift round with your hands and center over parchment-draped bowl. Gently press and pinch toffee against bowl to form a fluted bowl. Let toffee cool until rigid, 5 to 10 minutes.
Gently lift toffee bowl and paper from mold; remove paper. Slide spatula under smaller piece of toffee, and break it into large chunks for topping.
Fill bowl with frozen scoops and push topping into them. Drizzle with caramel sauce. Break bowl and serve with its contents.