Spread the oatmeal and chopped walnuts in a large baking dish and toast in a 180°C/350°F oven for 10-15 minutes until golden and fragrant. Stir them once to make sure they toast evenly. Keep a close eye on them - the walnuts can quickly burn if left too long in the oven.
In a large mixing bowl or in the bowl of your food processor, combine the toasted oatmeal and walnuts with the sesame seeds and shredded coconut. Mix it/pulse it all well together.
Add in the finely chopped dates and the peanut butter. Mix together first with a wooden spoon and then with your hands - this will require some muscle power. Alternatively, pulse the mixture in the food processor until it starts to come together.
Squeeze some of the mixture together in your hands as if you were trying to make a snowball. If it sticks together, it is ready to go into the molds. If it still feels crumbly, add some more dates or peanut butter (or both) until it starts to stick together.
Transfer the granola bar mix to a container lined with baking paper. You could use an old shoe box, a cake tin, or a plastic food container. It is best if your container has square corners because it makes it easier to cut the granola mix into bars later on. Your mix should make a block about 1-1 1/2 inch thick for ease of cutting it into bars or squares.
Press down firmly on the mix with the back of a metal spoon or with your hand until it is evenly flat.
Place a sheet of baking paper on top of your granola mix in the container and press down evenly with something heavy. I used another matching loaf pan to place on top and I weighed it down with a bucket of beans. In the past I used a couple of heavy books with equally good results. Basically you want something that will fit the container you are using for the granola bars so you can flatten the mixture evenly, and then something heavy to go on top of that. Keep it on for about an hour.
After the granola mix has been pressed for about an hour, remove the weight and place the container with the granola in the fridge to chill for at least an hour. Then remove from the fridge and cut it into the size of bars you want. These bars are very filling so I prefer to cut them into small squares rather than the usual bar shape, so they are small enough for my young kids to eat.