Combine flour and eggs; mix until smooth. Add milk, soda water, vegetable oil, and salt; mix to combine. Refrigerate batter overnight.

Heat a lightly greased skillet over medium heat. Remove batter from refrigerator; mix well. Pour 1/4 cup batter into skillet; cook about 1 minute. Flip crêpe; cook until golden brown, about 1 minute more. Transfer crêpe to a sheet of waxed paper. Repeat with remaining batter, stacking crêpes separated by waxed paper.

Combine almonds, 1/2 cup sugar, milk, rum, and vanilla extract in a saucepan. Cook and stir over low heat until sugar is dissolved and filling is creamy. Cool slightly before filling crêpes.

Combine 1/2 cup sugar, chocolate, and water in a saucepan over low heat; cook just until chocolate melts. Remove pan from heat; add margarine, stirring topping until melted and combined.

Spread 1 heaping tablespoon almond filling onto each crêpe. Roll up to enclose; place on a platter. Pour chocolate topping over rolled crêpes. Warm the platter in a microwave for about 30 seconds before serving if desired.