Grind all spice paste in a food processor, set aside.
Drain the dried shrimps. Separately, place in food processor and grind till fine.
In a wok or a saucepan, heat ¼ cup canola oil on medium high. Fry paste till fragrant, red and oil has separated, about 7-10 minutes.
Add more oil if necessary to prevent sticking.
Add the dried shrimp and sugar. Fry until aromatic, about 5 minutes. Add tamarind liquid. Continue cooking, adding more oil if necessary for another 10 minutes until the sambal is a dry and deep red in color.
Slice cucumber into thin rounds
Remove bread crust, and place two slices of bread on a cutting board. Generously smear butter on one side of each slice of bread.
Spread on a thin layer of the sambal, top with cucumber and sandwich with buttered bread.
Cut bread into 4 diagonally, making 4 tiny triangles.