Preparation

For the Champagne layer:

• Put the water in a small saucepan, sprinkle the gelatin on top, and leave to soften, about 3 minutes. Add the sugar and cook over medium-low heat, stirring to dissolve the sugar and melt the gelatin (don’t let it boil). In a medium bowl, combine the gelatin mixture and Champagne. Set the bowl over ice and chill, stirring often, until it reaches the consistency of unbeaten egg whites. Carefully stir in the sliced strawberries.
• Meanwhile, set a loaf pan in the refrigerator so that it’s tilted at a 45-degree angle. (Use a wedge of cheese, sticks of butter, or something similar to prop up the pan.) Pour the Champagne mixture into the pan. Let sit until just set, about 2 hours.

For the strawberry layer:

• In a small saucepan, soften the gelatin in the 2 Tbs. Champagne, about 3 minutes. Set the pan over low heat and heat to dissolve the gelatin. Purée the berries with the lemon juice, add the sugar to taste, and then strain the mixture through a fine sieve. Whisk the softened gelatin into the strawberry purée.
• Once the Champagne layer has almost set, set the loaf pan on a level surface (preferably in the refrigerator so that it won’t have to be moved) and carefully pour in the strawberry purée. Refrigerate at least 6 hours but preferably overnight. To unmold the terrine, cover a cutting board with waxed paper, dip the loaf pan quickly into hot water, and invert it onto the board. Slice the terrine into 1/2-inch portions; garnish with sliced fresh strawberries, if you like.