In large saucepan, toss together strawberries, rhubarb, sugar and vanilla. Place over medium heat and cook, stirring frequently until mixture is thickened and reduced, about 12-15 minutes.
Spread 2 tablespoons of butter onto slices of bread. Spoon compote on 4 of slices, on top of butter.
In large skillet or fry pan, heat remaining butter over medium heat.
In wide shallow bowl or pan whisk together eggs and milk. Dip compote-topped slices into egg mixture (but do not submerge it) and transfer to hot skillet. Dip remaining slices butter-side up into egg mixture and place butter-side down on top of compote-topped slices. Cook on each side 2-3 minutes until golden brown.
Serve immediately with whipped cream, additional strawberries and powdered sugar, if desired