Heat oven to 375 F. Spray a 9-inch round cake pan with cooking spray and flour lightly.
In a large bowl, sift the flour, baking soda and salt together. Set aside. In a small bowl, mix chia seeds with water and set aside to gel.
Slowly melt unsweetened dark chocolate and then allow it to cool slightly. Be careful not to allow it to harden.
In a large bowl, beat butter with yams, brown sugar, applesauce and honey for 2 minutes. Add chia gel and beat for an additional 2 minutes. Beat in vanilla and then chocolate. Gradually stir in half the flour mixture and then half the yogurt. Repeat with the remaining flour mixture and yogurt. Slowly and carefully stir in the boiling water. Pour the batter into cake pan.
Bake for about 20 minutes. Test cake with a toothpick — it should come out wet but not gooey. Do not over bake.
Cool in pan on a rack for 20 minutes. Remove cake from pan and cut into 12 pieces. Melt chocolate bar, drizzle over cake. Place on plates and garnish with strawberries and cinnamon.