In a pan large enough for 2 or 4 apples, add enough sugar and water in the above proportions to cover the apples (start with the given amounts and add more as necessary depending on the size and shape of your pan). Bring to a boil, and simmer a few minutes, stirring to dissolve all the sugar. Add the lemon juice.
Peel and core the apples. If you like, reserve the peelings for step 3. Add the apples to the simmering syrup (you can add all 4 at once if you like, but I find it easier to cook 2 at a time and peel the remaining apples while I wait). Simmer the apples until they are just soft enough to poke with a fork, about 5-10 minutes depending on their size and ripeness. Be sure not to overcook them! Remove and allow to cool.
Add the reserved peelings to the syrup (optional), and continue to simmer the mixture until it is reduced by half (about 20-30 minutes). Remove the peelings and cool the syrup, then chill it. The syrup may be stored in the same container as the apples after it is chilled, or it can be kept separately.
Meanwhile, coarsely chop the walnuts (some people use a mixture of walnuts and hazelnuts. I personally think it tastes best with walnuts only) and raisins together, and stuff the apples with the mixture when they are cool enough to handle. Chill until ready to serve.
Serve the apples cold in individual bowls with some of their syrup, topped with whipped cream.